Aww...just give them a salt tablet and tell them to suck it up.
just kidding...
Kids are told to take a drink during the school day every time they pass a water fountain, whether they are cutting weight or not. During practice, we take one scheduled water break during the practice. Everybody runs and we send them to the fountain by classes starting with freshman up through seniors. The longer they "hang" on the fountain, they longer they run. When we round-robin wrestle, they can get a drink only having wrestled for at least six minutes and only when its not their turn to be in. Most kids don't even bother. If they're not back for their turn in time, they run extra. I, on the other hand, pretty much take a drink whenever I want.