I agree with the last person, as sauna helped me a lot. I suggest you try it, when you have access to one. By the way, I had the same problem – brain fog during exam period.
Also, try other alternative (=not too harsh) detox methods, like increasing water intake, taking long walks in fresh air. And start the day with a glass of hot water (with lemon, if you wish) and contrast showers. Makes you really fresh and helps with the brain fog. At least it worked for me!