If you're not averse to canned food, that gives you loads of variety. You don't even have to eat them cold since you have a microwave. Pastas, beans, soups (yes you can eat condensed [or not condensed] soups cold, tastes fine), whatever. I keep stuff like that for emergency breakfasts.

You'll just need to buy cans with self-openers and bring cutlery (disposable or not).