Anyone who's been through college can answer this question quite easily.
It consists of a diet of basic food such as rice, noodles, ramen, etc.
Just focus on buying things from a local farmers market and eating lots of cheap grains such as rice, noodles, bread, etc. to fill you up.
It's recommended to steer clear of things like ramen (which are quite unhealthy), but once in a while, ramen can prove efficient.