TEAM RABOBANK has a secret: During the Tour de France, there has been something unusual splashing around in their drink bottles. No, it wasn't the latest BALCO chemistry experiment. And it had no label or brand. It was a home-brewed concoction so powerful it may well change how athletes drink for the most grueling endurance races. Best of all, the recipe is so simple you can make it in your kitchen.

The mystery drink defies long-held training dogma. Until recently, sports nutritionists had been unequivocal: Your body can absorb only so much sugar (read: energy), and that limit is 60 grams per hour. No matter how many gels and cups of Gatorade you suck down, your body can burn only about one gram of sugar per minute, with the rest just sloshing around in your gut and possibly causing problems. (Porta-Potty, anyone?)

But in 2002, Asker Jeukendrup, a 38-year-old Dutch nutritionist, triathlete, and Team Rabobank consultant, made an intriguing discovery. In his lab at England's University of Birmingham, cyclists drank a syrupy cocktail of two different sugars—glucose and fructose—blended in a two-to-one ratio. Jeukendrup's theory was that the cyclists' bodies would use independent systems to digest each sugar, so the cumulative energy uptake would be greater than what you'd get with a single sugar. And he was right. Test subjects were able to burn through 75 grams of carbs per hour, with subsequent studies achieving rates as high as 105 grams per hour—75 percent more than what had ever been measured.

"It's probably a real phenomenon," says University of Texas at Austin exercise physiologist Edward Coyle, the nutritionist for the San Antonio Spurs. "The question is, will these sugars allow athletes to exercise at higher intensities or run faster? That's possible but still needs to be proven."

Jeukendrup's most recent research, presented at a conference in Denver last spring, attempts to do just that. The study found that cyclists drinking the 2:1 sugar mixture for a three-to-five-hour ride maintained higher pedal cadences and reported less fatigue than those drinking a pure glucose drink with the same calories. (The benefit is maximized on longer workouts, but there's no downside on shorter outings.) It's preliminary evidence, to be sure, but there are already plenty of believers. Team Rabobank quietly used Jeukendrup's custom mix for several years. In 2006, PowerBar reformulated its line of drinks and gels based on Jeukendrup's science. (The company started funding his research earlier this year.) Jeukendrup himself uses the mixture for his own races, like last year's Ironman World Championship, which he finished in a respectable 10 hours 49 minutes.

Until other labs replicate Jeukendrup's results, don't expect a radical remix of your favorite sports drink. Even then, different formulas might be better suited to different workouts (see "Energizers," opposite). Jeukendrup himself says there might be a slightly more powerful mixture out there—that this is just the beginning. The best tester? You. (See "Secret Formula," above.) The drink's ingredients are cheap and readily available at health-food stores, and the DIY approach allows you to customize taste—one reason athletes don't drink enough in the first place. If nothing else, you'll be on the cutting edge, which is a very sweet spot.

The Rules: For any race, says Jeukendrup, follow these hydration tips
1. Use a calculator to determine precisely how much liquid and fuel you'll need hourly. And make a plan for how you'll get it.
2. Don't experiment with a new drink on race day. Find out what's at the aid stations, which sports drink is offered, and how much it's diluted. Alternatively, bring your own or pack salty gels and just drink the water.
3. Track your intake during the race, and stay on schedule.
4. Never skip breakfast. You won't be able to replace those calories mid-race, no matter how much fuel you drink.