>>14065106anything tasty, but in a small enough portion that I'll leave off a bit hungry, rather than satiated. Granola, trail mix... type of snack is an easy way to maintain a baseline. Usually have water with all things. Sometimes have coffee as well.
Things like 'cornsyrup treats' or sodas depend on the level of physical exertion (am I in a recliner studying?, or is there a physical element; groups, walking, talking, intermittent activity or even exercise breaks).
/these answers are suited to my own process, and not meant as advice.