I've seen a few healthy choices...but not necessarilly gluten free, LOL. (Crackers, granola bars)

I've seen some stocked with apples, but they bruise when they fall.

I'm thinking LARA bars would be good, small cups or tubes of applesauce, rice crackers, boxes of raisins, String cheese if you have refrigeration, single serve boxes of cereal, possibly "just add hot water" meals, and dried fruit or fruit and nut mixes all would be good bets. Packs of Instant Oatmeal for non gf folks? Juice boxes or soy milk boxes?

And of course...water and juice in the soda machines