Lunch Ideas, no microwave or fridge

Hello! I'm a college student and doing work-study over the summer. I've been trying to create lunch meals for my breaks, but the issue is that the building I am in is locked and need my supervisor to let me back in when I leave. This makes microwave meals difficult since I have to walk to a different building to heat up my food. I've been doing pb&j (fake pb since I am allergic) and have been struggling to find good and easy meals to have. Any ideas help and I would be so grateful since it's less of a hassle to eat during lunch!