I'm not going to give you any tips on how to memorize formulas. I'm not going to tell you how you what to eat during your lunch break.
I just have one word for you: coffee.
Maybe Red Bull or some other energy drink is your preferred source of caffeine. But whatever it is, drink it up!
Test-takers are often told that they have an average of 90 seconds to spend on each question (120 questions for each 3-hour section). At least that's what they told me when I took the cram courses.
As such, bathroom breaks are often considered wastes of time.
But that's a fatal error.
Drink coffee, Red Bull, or whatever, and give yourself 5 minutes for a bathroom break for each section.
It's better to be efficient for 5 hours and 50 minutes, then to be inefficient for 6 hours.
Sincerely,
Someone who sat through and passed all three exams
PS: And don't wear a diaper. Every CFA test-taker has heard someone joke about this, and some claim they know someone who's done it. But that's ridiculous.