When it comes to food, the college student stereotype can usually be summed up by a package of ramen. It's cheap, it's filling, and it's easy to make.
Unfortunately, your body won't be on board with this logic forever. Eventually, you may have to eat a vegetable. You could buy a package of raw carrots and eat them whenever you get hungry, but it's probably more beneficial to learn how to cook a few basic meals. You can modify them to get all the nutritients you need, and they're going to be a lot cheaper than fast food in the long run.