We all know the answer to this. Alfred keeps a large supply of BatCoke for him in the Bat Cave
He’s the CEO so obviously he has not much actual work to do.
I cannot wait for Absolute to touch on this. We’ve already seen that he’s more brutal, but I really want to see how they handle the weight of the double life without all the training and “I can powernap for 15 seconds with my eyes open and get enough rest for a month”.
Short answer: mental illness
Long answer: it will vary from various iterations, but often Bruce Wayne is minimally present as a CEO (which, eyy, not really different from most of them.) Bruce Wayne / Batman is able to rest while crime exists in the same way an insomniac rests on itchy sheets in the middle of a parade: he doesn’t. He is beyond obsessed on stopping crime, to the detriment of his health and safety, as well as those around him. His entire entourage regularly pushes him to slow down, rest, take time to heal, etc, and he keeps getting up. It’s beyond his (present) ability to control. There’s been a few instances (like with Andrea in Mask of the Phantasm) where he does find himself at peace and can move on, but mostly, he’s a prisoner of his own trauma. It’s been stated multiple times that his obsession is no different than the Joker’s or the Riddler’s.