This is a very bad idea, because the concentration will drop to almost zero, and the point, as I understand it, is to siphon off as many resources as possible during these 2 days. Therefore, I advise you to do this:
1) often and eat little, but low-fat food. It is advised to eat sweets, but this can have the opposite effect and, moreover, is harmful. Heavy food makes you sleepy, and constant chewing, oddly enough, helps you stay awake. Apple slices, carrot sticks, nuts will do.
2) You will still have to sleep. It's better to make yourself a schedule, for example, I sleep for half an hour every 4 hours, or I sleep for an hour every 6 hours. This will allow you to reboot and relax, and maintain at least some concentration.
3) Phenotropil. For emergency, the very thing sold in the pharmacy without a prescription, increases productivity, increases attention, reduces sleepiness.
How dumb. The main thing is to keep yourself busy with something that makes your head work, from solitaire games to some serious activity. No monotonous actions like scrolling through the tape or watching anything, and it's better not to be in a lying / sitting position at all. Ideally, of course, be outside the home, that is, where there is no way to fall asleep by accident. The most dangerous thing is when you have a thought: "What the fuck is this, in fact, fucked up?" If this is preparation for exams, then you need to stock up on coffee after all. It is better to alternate preparation with small physical activity, from time to time to be distracted by extraneous things so as not to stick. And if it's really bad, then you need to sleep for 15-20 minutes, but immediately after waking up there will be such a state as if you were chewed and spat out, but after that it will become much better. The main thing is not to get carried away and take care to wake up after this break. Good luck.