In addition to sandwiches, cereal, and fruit in your room, my suggestion would be to make your own trail mix with unsalted nuts and dried fruit (without added sugar or sulfur). Trail mix doesn't need refrigeration, it contains lots of nutrition for the amount of space, it can tolerate getting swashed, and a little goes a long way. That way, you can carry a ziplock bag of the trail mix with you and have a quick snack any time you need it without having to go all the way back to the room. I also recommend bags of baby carrots. They're still edible without refrigeration.