If you really want to eat cheap, but still eat something that has some nutrition, then buy potatoes, chicken pieces and frozen mixed veggies. Wash the chicken, salt it and stick it into the oven to bake at 350 degrees. Wash a potato and stick it in the oven to bake. Chicken and potato should both take about an hour. Or microwave the potato...takes 4 minutes. Frozen veggies take 3-4 minutes as well. It's all easy, cheap and still has nutrition.

If you don't want nutrition...eat a hot dog. Some fast foods might sound inexpensive, but I think that in the long run they still end up costing more than buying some of your own groceries and cooking them. So save that fast food money for your beer.