The Claim: Offers an extra-powerful vitamin hit because of the cap-based storage system.
What's in it: Fifty milligrams of coconut water, plus vitamins A, B5, B12, C, and E
When it works: After a libation-fueled night. Dehydration is a top cause of hangovers; coconut water is an excellent rehydrator.
On the other hand: Vitamins do lose potency, but Christopher Mohr, R.D., cofounder of the fitness consultancy Mohr Results, Inc., says storing them in the cap won't boost quality.


The Claim: Works like coffee, tea, or Red Bull.
What's in it: Nothing but water and caffeine, either 45 (akin to tea or soda) or 90 milligrams (coffee, energy drinks)
When it works: Anytime you're sluggish—it's healthier than soda and easier to tote than a coffee mug. "This is a fix for people worried about coffee stains or additives in cola," Cohn says.
On the other hand: As with all caffeinated beverages, too much (we're talking more than 500 milligrams a day) can lead to insomnia, stomach issues, and muscle tremors.


The Claim: Speeds recovery and ups strength.
What's in it: Ten grams of whey-protein isolate
When it works: Après exercise, especially strength-based routines. Whey protein is high in amino acids, which help muscles grow and repair.
On the other hand: Most experts say 20 grams of protein is ideal post-workout; this has 10. Follow up with Greek yogurt or almonds.


The Claim: Combats acidic waste thanks to its pH of 9—tap water is 7—and hydrates like a sports drink.
What's in it: A proprietary mix of "72 bioavailable electrolytes"
When it works: During long training sessions when you're sweating profusely and need to replenish electrolytes. Fitness fanatics Diddy and Mark Wahlberg are investors.
On the other hand: Experts call B.S. on the acidity assertions: "Your stomach's pH of 2 will completely neutralize that water," Cohn says.


The Claim: Supports the immune system.
What's in it: Vitamin C, zinc, and taurine
When it works: If you're feeling congested. At 150 percent of the recommended daily dose of vitamin C, it packs a potential cold-busting punch.
On the other hand: Cohn says nutrients from food are more readily absorbed, processed, and digested. Mohr concurs: "You'll do better eating an orange."


The Claim: Helps you doze off easily.
What's in it: The neurotransmitter gamma-aminobutyric acid (GABA) and melatonin
When it works: Before you hit the sack. GABA reduces stress, and there's solid data on melatonin's sleep-inducing qualities.
On the other hand: Don't gulp it under the influence of alcohol or antidepressants: Mixed with either, it may spike your blood pressure or heart rate, says Cohn.

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The Trend: Bespoke Sports Drinks

First came sneakers—now you can personalize your sports drink. Infinit Nutrition asks how you train, how salty you get (minimal to crusty), and how often you cramp up, then, for $2 to $3 per serving, creates a custom combo of protein, carbs, caffeine, and sugar. Willing to spend for bigger promises? Shell out up to $3,500 for 16 ounces of a tailor-made formula from PerformanceDrink. "Results jump at least 5 percent," claims founder Paul Booth. He won't reveal ingredients, except that they're "all legal." Cohn is skeptical: "Olympic and NCAA screenings have been done, so it's safe. But without peer-reviewed research, the performance-improvement claim is unsubstantiated."

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Also on Details.com:
The 9 Best New Water Bottles
Meet the Futurists
5 Hydration Myths Debunked