I have tried several brain/mind stimulant. Coffee, Kola Nut, Chew Gum, Alcohol e.t.c. But what has worked best is the euphoria that comes from breaking limits or conquering resistance. What works best for you?
Coffee does the opposite for me. A small quantity of alcohol and then right after consuming it gives a great stimulus. But best really seems to be doing something 'different' but also brain stimulating; after 1 hour of programming, I try to learn Spanish or get out any of the great formal method books, after 30 minutes of that, my brain is better at programming.