Of 13 drinks tested, the sports drink did not beat water
Seventy-two men each drank a litre and gave four hours of urine. A rehydration solution and both milks retained more fluid than still water; the sports drink did not.
What the study found
A sports drink held on to no more fluid than plain water
Thirteen everyday drinks went through one test and three passed. Seventy-two men drank a litre each and gave four hours of urine: a rehydration solution and both milks retained more fluid than still water, cutting that from 1,337 grams to about 1,050. The sports drink did not.
The caveat · Men drank while already hydrated
The men were fully hydrated and fasted when they drank, which is nobody's state when they reach for one of these, and retention behaves differently in someone already short of fluid. All 72 were male. The outcome is urine volume over four hours, a stand-in for retention rather than for feeling or performing better. The drinks were not matched for sodium, so this ranks these particular products, not electrolytes as an idea.