Yeah it depends on your spice rack and whatnot but if it were me, I'd be buying eggs, flour, tomatoes/tomato sauce and make some spaghetti, or buy some stewed tomatoes, beans, rice, tortillas, things of that nature.
All depends on what else is in your fridge and in your cupboards, you can make a lot of really good stuff with 20 bucks if it's just you to feed. If it's more than you... just make spaghetti or chili.
The Life of the Knife is Ended By! The Wife.