Not a doctor, but based on research I’ve seent brain fog (in likely many cases) seems to be due to inflammation. autoimmuneinstitute.org/…/brain-fog-likely-caused…

Have your friend try inflammation-reducing drugs like metformin. Metformin specifically, maybe there’s others, I’m sadly not a doctor. Metformin is a magic drug that’s not just for diabetius.

It won’t be immediate, but maybe it could help your friend recover. Idk if cranking yourself will break through when it’s a blocking mechanism causing the problem.