All beards are not the same ;-). I am the ashwagandha, brahmi, arjuna, gotukal and whole lotta other brain enhancing herbs and roots drinking kind of bearded guy :-P.
Coffee affects your adrenalins in the long run, then you need coffee just to stay normal, forget about any enhancement. I will never take such a risk.
Green tea for convenience but nothing beats these concoction of herbs to get your brain working fast without any side effects