EFS Drink Mix

$34.99 USD


This spring, we’re updating EFS for faster uptake with an uptick in carbs per serving. Transitioning from current to new won’t be a gut punch – in fact, just the opposite. The new EFS prioritizes three things: delivering more fuel with minimal GI distress, keeping you hydrated, and preventing cramps. Everything else has been stripped from the formula; it’s purely purpose driven for pure performance results.

✓ Increased Carbohydrate Content
✓ Increased Electrolyte Content
✓ Streamlined Formula for Faster Uptake

ETA 4.30.24



The latest research shows you can almost double the amount of carbohydrates that can be absorbed without GI distress when fueling with Multiple Transportable Carbohydrates (MTC’s) in specific ratios. The key is to consume specific carbohydrates in the right ratios.

Powered by advanced fuel-source technology, EFS was engineered to maximize carbohydrate utilization by delivering a precise combination of MTC's, glucose and sucrose for next-level endurance you’ll notice the first time you use it.

"When you nail your fueling it's pretty remarkable to see that you can actually get stronger as the race unfolds."
Hannah Otto

Leadville 100 Champion (2022)



We know how frustrating it is to have your day wrecked because you’re seized up with debilitating muscle cramps. It’s the number one issue most athletes face.

Unlike most drink mixes, EFS delivers a clinically effective dose of all 5 electrolytes (sodium, potassium, chloride, calcium, magnesium) in the levels shown to prevent cramping.

Total electrolyte content (Na, Ca, Mg, Cl, K+) in mg
Based on 1 serving (12/23)


“The latest EFS formula is a breakthrough in sports hydration. With more electrolytes than competitors and ingredients to improve mental focus, you’ll finish the race as strong as you started.”

Phil Gaimon (2x World Hillclimb Champion)

Rapid rehydration


We spared no expense upgrading the EFS drink mix, investing in the latest research-driven innovation and technology. Our scienficially formulated, isotonic formula quickly replaces the fluid and electrolytes lost during exercise to ensure optimal hydration, preventing the onset of fatigue, and improving peak performance.

Pro Tip: For best results have a serving of EFS 30 minutes prior to training and racing.



The brain plays an essential role in endurance and performance. Mental toughness and presence of mind are equally as important as fitness. You have to be able to suffer and handle stress when your body is begging you to stop.

That’s why the reimagined EFS includes Suntheanine ®, a patented innovation that gives you the mental toughness you need to push further and find a gear you didn’t know you had.

Suntheanine® is protected by over 40 U.S. and international patents for its various physiological efficacies and L-isomer specific production processes.



Research shows BCAAs taken during exercise – not before or after – keep the flow of fuel sources from carbs and fats mobilized and upsized when you need them the most.The final sprint, the push to the summit, grinding out the last interval - BCAAs are critical when you’re on the limit but there’s still more work to do. In EFS, BCAAs unlock a final emergency fuel source when all other options – and all of your competitors – are exhausted.

"The new EFS drink mix tastes great, helps keep you focused during long and hard training sessions, and fuels the body properly."
Matt Hanson

5x IRONMAN / 5x 70.3 Champion / Holds the record for the fastest full-distance IRONMAN (7:39:25)


Suntheanine® boosts mental toughness to help you push through suffering

Prevents cramping and dehydration—delivers 1160mg of electrolytes

Carbs from multiple sources provide immediate and sustained fuel

7% osmolality ensures bioavailability and reduces GI distress

Citric and malic acids promote oxygen uptake and energy production

New taste profile eliminates the flavor vs function compromise


EFS provides everything you need to maximize endurance and performance. Our industry-leading electrolyte levels help you stay hydrated and avoid cramping.

With the latest amino acid technology and ideal carbohydrate sources, EFS refuels working muscles faster than ever. Plus, the new flavor technology eliminates the formula over flavor compromise.

With EFS, you can train and race with confidence knowing you don’t have to worry about gaps in your nutrition.

"Beyond the importance of Suntheanine, I think the new flavors are the biggest advancement."
Jeffrey Rocco, MD


EFS is for use during exercise to prevent cramps, maintain fuel levels, and support mental toughness when it’s needed most. It can be supplemented with Liquid Shots before and during an event, and Ultragen helps consolidate gains during recovery between sessions. 

Regardless of your training load, a daily dose of our MultiV and Optygen lines help you lay a foundation to achieve your goals.

"On-the-bike taste was great. I felt amazing on the bike today! I had a PR on the top half of the climb. Surprised by this, because I had skied hard the day before."
Doug Davis

Cat I Cyclist


From the carbohydrates (osmotically balanced with your body in a 7% solution) to the electrolytes (20-100% better absorption rates), every ingredient in EFS is selected and portioned for faster and easier absorption without GI distress.

The inclusion of citric and malic acids also encourages oxygen uptake and production of ATP (the body’s energy source), helping your cells use the fuel once it’s delivered.


We prioritize purity by using only Suntheanine, the original and cleanest L-theanine, and free-form amino acids, which have a purity level of 99-100%.

We also omit ingredients with no value—even the ubiquitous vitamin C, which features in virtually every other mix despite research that shows it reduces endurance when taken during exercise. EFS still provides immune system support courtesy of theanine, just without impacting performance.


Our approach to product design eschews unexamined ingredients, traditional processes, and trendy minimalism in favor of research-based innovation, premium ingredient sourcing, and the uncompromising expectations of elite athletes. We’re always ready to show our work and support our products with the scientific literature that informs our design choices, but we also know what virtually every athlete and publication using or reviewing our products learns firsthand: First Endurance products speak for themselves, and you can feel the difference right away.


Supplement Facts
Serving Size: 1 scoop (32 g)
Servings per Container: 30
Amount Per Serving %DV
Calories-110 Calories from fat-0
Total Carbohydrate 26 g 9%
Sugars 16 g **
Calcium (as DiCalcium Malate) 100 mg 8%
Magnesium (DiMagnesium Malate) 150 mg 36%
Chloride (as sodium chloride) 450 mg 20%
Sodium (as sodium chloride) 300 mg 13%
Potassium (as di-potassium phosphate) 160 mg 3%
L-Glutamine 1750 mg *
Branched Chain Amino Acids (L-Leucine, L-Isoleucine, L-Valine) 250 mg *
L-Theanine 50 mg *
*Daily Value Not Established
**Percent Daily Values are based on a 2,000 calorie diet.
Other ingredients: Sucrose, Maltodextrin, Glucose, Citric Acid, Natural Flavor, Stevia Extract.


Q: How is EFS different than EFS-PRO?

 A: Though EFS is itself a step above the competition, EFS-PRO supports the most demanding efforts in the most extreme conditions by providing 2x more carbs and more electrolytes/serving. 

Q: Are there other benefits to drinking EFS or EFS-PRO, besides for training and racing?

A: Absolutely. EFS and EFS-PRO can be used to top off glycogen and electrolyte levels before an event or race.

 Q: Is EFS gluten free?

A: Yes, EFS and EFS-PRO are both gluten free.

 Q: Do EFS or EFS-PRO have any artificial flavors or colors?

A: No, but it tastes so good you’d be forgiven for thinking we were cheating.

 Q: Do I need to take a full serving of EFS or EFS-PRO to get a benefit? 

A: No. A higher concentration increases calories and electrolytes. While our recommended serving concentration is designed to maximize theanine’s effects in a steady dose, ingesting reduced amounts will still produce a proportionally scaled effect in terms of promoting calm focus. In other words, if you are a smaller person and normally consume a somewhat reduced amount, you will still get the same benefits.

 Q: Do EFS or EFS-PRO have any stimulants in it?

No. In fact, it does the opposite, calming you down and maintaining a cool, collected approach to whatever you’re doing, whether that’s racing, training, or resting up the night before an event.

 Q: Can I use EFS and EFS-PRO with caffeine?

Yes. There are no counter-effects from caffeine consumption that you’ve established through your daily caffeine habit—err, intake. Keep drinking tea or coffee as usual. 

 Q: How much EFS should I use during my training and racing?

 A: Consume one serving
30 minutes before exercise. Use as needed during exercise.Additional calories and electrolytes can be added with Liquid Shots.

 Q: How should I mix EFS?

SMALL SERVING: Mix 1 scoop with 21-22oz of water

LARGE SERVING: Mix 1 ¼ scoop with 24-26oz of water

Q: Is EFS vegan friendly?
A: Yes.

Q: Is EFS gluten-free?
A: Yes.

Q: What's the glucose:frucose ratio in the formula?

A: The glucose: fructose ratio in the EFS formula is  6:1 Glc:Fru.

Q: Is there any way to get too much Theanine from EFS?

A: Only if you macro-dose (200mg or more in a single or repeated shot). Even if theanine is administered in a single macro-dose, the effect is just a too-calm calm that fades as the theanine leaves your body—Nothing serious or harmful. Click here to learn more about dosing and uptake. That’s because theanine is water-soluble, it metabolizes fast and doesn’t accumulate . Once ingested, it’s half gone after 60-90 minutes, and it’s gone completely in 24 hours.  

 Q: Does EFS or EFS-PRO help me hydrate better than water?

A: We won’t name them, but there’s a growing list of competitors in the sports hydration game making the claim that their product hydrates better or faster than water alone. This is a so-what claim predicated on evidence that not only doesn’t apply to endurance athletics, but actually hampers performance during long-term endurance events. For their rationale and claims support these companies cite WHO and other medical guidelines for treating serious dehydration in disease and severe exposure conditions, not the sports nutrition guidelines for healthy athletes in endurance competitions. Also important is the need for more fuel, and these drinks fall short in the fuel department. Check out Dr. Bucci’s extended consideration of these claims here.

 Q: I’ve heard that there are benefits to having protein during exercise. Why doesn’t EFS contain protein?

A: EFS contains 2g free form amino acids per serving which is the equivalent in BCAA and glutamine profile to 9g whey protein. Protein naturally contains BCAAs and glutamine.

Clinical evidence supporting the use of BCAAs and glutamine during exercise dates back to 1991. These clinical studies clearly indicate supplementing with as little as 1g free form amino acids improved performance, reduced post-exercise muscle damage, improved muscle glycogen resynthesis, reduced central fatigue and improved rate of perceived exertion. These are the same claims made by the most recent protein study and clearly support a mechanism for improved performance.

In addition to the clinical support, other factors lead to a decision to use these free form amino acids over complete proteins.

Proteins are more difficult to digest than amino acids during exercise, they don’t taste very good during exercise, and they can reduce the glycemic index of a drink, further reducing its ability to be quickly absorbed. There is considerably more evidence supporting free form amino acids than complete protein

 Q: Are EFS and EFS-PRO safe for kids?

Yes. Just make sure they pay it back during their turns at the front. 

 Q: I am prone to cramping during longer training and racing. Will EFS help me with cramping and dehydration problems?

A: Yes, cramping stems from electrolyte imbalance, electrolyte depletion and/or dehydration. EFS provides a clinically-effective dose (of all 5 key electrolytes) to prevent cramping and dehydration. The combination of all five electrolytes delivers a potent 1160mg per serving, helping to prevent cramping. The 300mg sodium per serving also aids in maximum fluid absorption so you stay hydrated throughout your training and racing. Supplementing with additional salt tabs, electrolyte tabs, or salty snacks is not necessary with EFS.