Give it to them of course (even without the hot temperatures). Saw a game (temp was probably 80F) where AR motioned to CR to give a water break and CR waved him off. In last two minutes of the game, player feints on the field and ambulance had to be called. Always error on the side of safety. After all these are children.
Calling a water break though would have been unfair to the other team whose girls were in better shape, and worse yet it might of been a violation of the "system".