Whenever we have cereal but no milk left, I melt peanut butter in a bowl in the microwave and mix it into my cereal. Then again, I usually just eat peanut butter plain when we're low on food :3 It works with chocolate, too, but nobody I've told this to ever thinks it sounds even remotely good
When I was 7 or 8 we used to make scrambled eggs in the microwave because we weren't allowed to use the stove yet. Crack an egg into a cup, stir it up, add salt/pepper, and stick in the microwave for a minute. CLEAN THE CUP IMMEDIATELY AFTER YOU FINISH EATING OR THE EGG WILL RUIN IT FOREVER. Hahah, my parents started cooking eggs for us whenever we asked after we ruined a couple of cups that way >.>
Pretty much everything is good if you mix it into mashed potatoes.
We used to make cinnamon toast for breakfast all the time because there's virtually no clean-up like there is for fancy things like French toast - just butter the toast and sprinkle brown sugar and cinnamon on it. Toast in toaster oven or microwave (don't use a pop-up toaster because the brown sugar will fall off into it).
Grilled cheese is a college kid staple, I think. I try to make it a little more interesting by adding garlic salt. I also like adding salami (cook it in a saucepan) because it tastes kind of like bacon
If you have a head of lettuce around that you can't seem to use up before it goes bad, try making wraps with lettuce instead of tortillas. Also cuts down on carbs, since so much of our cheap food is chock full of them