LPT Request: How to get rid of or reduce brain fog. Aka brain farts, brain fatigue, senior moments(not explicitly for seniors)

I did some googling, and all I found were pseudoscience-ish/alternative medicine/new age/vague/hardcore-stoner-in-a-colored-tent type of advice(Not saying it doesn't work, but it seems to be something that would improve your lifestyle more than anything I'm looking for). I've got a test tomorrow, and these past couple days this brain fog set in that makes it so that I stare at a paper trying to make sense of it for half an hour when the explanation is clearly on the paper. I also feel like I'm just viewing the world through a camera, I get a strange detached feel. This always happens when I get brain fog, which is strange.

It's so frustrating to have a big test the week you feel like you'd muck up putting on your shoes, but well, FML.

TL;DR: Having trouble accomplishing basic cognitive tasks and have general impaired thinking ability

EDIT: Holy crap, I just got back from school to this. RIP Inbox(hello there /r/circlejerk)