Practices from 12-4 on weekends when you do not have tournaments is a big help. Our girls are just used to it. We run through several cases of water on a weekend. They know by staying hydrated we will have a competitive advantage during the championship game.
Here in Tucson, it is just impossible for me to drink enough water. I have one of the big jugs from Thermos. I have found bananas, cold orange slices, and dill pickles help me. I feel like I need sodium. I also feel like I need Ringer's Lactate through an IV (seriously.)
A lot of athletes don't like to drink water, because then they need to urinate. But they really need to drink and use the bathroom, to be healthy.
We start hydration (water only) on Wednesday before a weekend tournament. I tell my girls that I want to see them urinating in the 9X's per day (Thursday & Friday) before the tournament. Sports drinks are to only be consumed after a game. We play in TN where it is not uncommon for temps to be in the mid to upper 90's with high humidity. Once we started this routine we have had little to no problems with headaches and dehydration. You can probably get by with less, but this is our goal.