I've worked in some tight backstage environments on large dance-heavy musicals with casts of 35 or so. Very typical strategy that I've used and seen is to buy a hanging shoe organizer for each side of the stage, and find a home where they can live, ideally close to either the stage entrances OR the water cooler. Cast are responsible for setting / refilling their own bottles, and can claim a "slot" in the organizer.
In addition to the shoe organizer, my theatre provided one-use 3 ounce cups at the coolers. I think this is the best of many worlds: it encourages an eco-friendly option, while still allowing anyone in the show a chance for a quick drink. It empowers cast to take responsibility for their own physical needs, and prevents the SM team from gaining additional "clean-up" work. And it's a space-saver: no need for a table surface at all. I've hung them from the side of prop-shelves, on the side of a backstage call-desk, the back of a dressing room door, and from the piping and infrastructure already present in the theatre.