you know i am going to tell you something that you won't like cause everyone wants a supplement or pill to take for everything.
but the answer to your question is SLEEP, eating healthy and exercise. also i will say that when i did my 10 day fast there was never a time that i thought so clearly. i think our brains are too reliant on things like sugar and caffeine to 'wake us up' when all along we should learn to use our brains in the first place