Students may bring water bottles and refill during the day.  They are also very hungry when they return from morning rotations and we have a quick snack.  This is something I pass out to the entire class, just a small handful of goldfish, pretzels, animal crackers, cheez-its, or something similar.  I don't have a snack schedule, but will just tell students we are about out of snacks and they will ask at home if they can bring something.  Individual snacks were not a happy thing (thats why we don't do them),  but classwide is!