For Finals it depends entirely with the type of exam.
Multiple Choice: You can simply create one by literally answering a question you feel will be on the exam. Even if you write a wrong answer – not on the exam of course – you can be sure that could be on the exam, but have the correct answer as needed.
Written: Get writing! Free write until you suddenly ask yourself if this is relevant and not too wordy. You also retain information more this way.
Case Exams: This is where it gets fun. I will assume you have had previous content knowledge, but this is your time to shine. If possible, think of scenarios what could be case studies in real life and see if it can be applied. Typically, I like to rehearse this orally in my mind because you also can figure out whether your communication was in sync with the case.
Food: Just drink water and I strongly would limit my coffee consumption.
Sleep: Any sleep is sleep, even for a few hours, but take naps in between. A friend helps when you can keep each other in check to take a nap.