I brewed tea out of the leaves and also chewed them when hiking in Peru. Stimulant level-wise it felt similar to green tea. Maybe also a slight euphoria when chewing them but it's definitely still way less potent than a coffee (atleast for me).

The only interesting side effect was that both my wife and I experienced tingling feet when combining coca leaves with acetazolamide, the altitude sickness meds we were taking (tingling feet is apparently a side effect of those meds). I wonder if on some level it does have a similar mechanism for altitude sickness?