It's been a while since I posted here, but this summer I took the Bar Exam and everyone recommended I wait until the exam was over because the added stress on the body (and mind) of fasting is not needed while you study. If you are set on fasting, I'd use The Master Cleanse
or Juice so you have energy to study. When you are done with exams, just imagine the relaxing fast you can have then! If you're trying to lose weight, studying burns calories!