2) He’s A Borderline Alcoholic
The only time Christian Bale’s Bruce Wayne ever appeared ‘drunk,’ he was merely pretending to be in order to clear his house of guests (so he could later have a fight with the League of Shadows, natch). In fairness to Affleck’s Bruce, he also tries the old ‘faking drunkenness as a ruse to carry out a secret task’ in Batman V Superman. There is, however, also a very strong suggestion that Affleck’s Wayne is a heavy drinker for real.
In one telling scene, Affleck awakes groggy in his swanky bachelor pad, presumably with a nagging hangover. Alfred picks up an empty bottle of wine, and asks whether Bruce will leave behind any of what’s left in the Wayne family wine cellar.
The implication is that Bruce begins a lot of his mornings like this, sore-headed after another night spent drowning his sorrows and dulling the nightmares. The bottom line is he’s a borderline alcoholic.