MCAT eating choices should begin two days in advance. Carboload for two days. I had pasta for two nights in a row. During the test I brought literally a huge bag of trail mix containing only lightly salted peanuts and raisins. Take it easy on the raisins though so you don't have to poop. The salt from the peanuts is helpful but again don't go overboard. For the main course (your 30 minute break) I recommend eating a healthy sub sandwich. Nothing with too much sauce. You may not even need to eat all of it if you are snacking on the trail mix.
The most important thing is that whatever you decide to eat, have it ready and in your fridge the night before you take the test! Best of luck and don't over think it. 😉
