If you feel comfortable fasting. I recommend you to take a low carb meal the day after. During the test, drink water and have a bag with salt on your pocket in case you feel weak. You just heed to be hydrated. Best of luck!
If you plan on waking up to eat something before dawn, it might be helpful to eat something full of fat and protein, food that’ll help you avoid a crash in the middle of the day. Anything carb-heavy might leave you wanting a nap halfway through your test. I’m not a huge fan of fatty things so I’m not the best at giving recommendations on that, but tuna is a good source of protein, if you like fish. Some CEOs swear by eating canned sardines in the morning. I’ve heard people like eating cuts of red meat like steak or goat for the fat and protein. If you’d like to avoid meat, maybe some fried tofu or eggs.