Oatmeal, peanut butter, and a cheap fruit like a banana will make you a hearty meal for pennies. Just combine the ingredients and let run for 1-2 minutes. No need for a fridge. It's got whole grains, nut protein, and a fruit.

Anything you can boil, you can also microwave. You can poach eggs in a cup and make rice in a bowl. Steamed veggies + rice + poached eggs make a good dinner or lunch. You could probably do beans as well.