I drink 3-4 espresso, without sugar or anything else added.
It wouldnt be too much, and I dont consume energy drink or other caffeinated drinks.
Frankly from some years the coffee I consume daytoday is pretty strong, and is like a double expresso; sometimes I'm far from home and consume espresso from random places, and even with 3-4 espresso I feel like I'm decaffeinated...