One of the often overlooked causes of Brain fog is gastrointestinal disoders, the gallbladder most especially, when it's not in shape will cause sharp pains to the right back of the neck up to the brain to cause brain fog.
I have had this problem for years and never understood the cause until i learn't about it from Dr Berg. Here is the link to the the video below
So you actually need to know the root cause of the brain fog, if not you would be treating the wrong still and wonder why you still feel the same. I was able to overcome this brain fog causes by my stomach by adjusting my diet and using the following herbs
If your stomach is not the problem then you can use nootropics, one the best is brainpill another one is noocube. You can check out both