Sleeping is just as important as the act of studying! I can understand where it is easier said than done to get enough sleep, but have you read some of the research that spans over the last 20 years? Research has found a correlation between sleep and test scores in that getting more regular nights of sleep can lead to improved test scores. Additionally, sleep can improve memory retention and recall by between 20 and 40 percent.
It's understandable that we can’t all be consistent with sleep every night, but what about the night before your BCBA exam? Have you planned out what the night before and morning of will look like? Consider planning to relax as best as possible (e.g., bubble bath, comedy television show, meditation, walk the dog, etc.) and get to bed early! When I created my plan, I set a cut off time for studying. At that point in your studying, you should be set. I ate a nice dinner, relaxed, and slept a full night of sleep.
What is your plan? How do you prioritize sleep?