What does Dolphus drink? Why?

Dolphus Raymond drinks Coca-Cola. He allows people to believe he is a drunk because it means they won't question his actions..... they just blame it on the alcohol.

“Wh—oh yes, you mean why do I pretend? Well, it’s very simple,” he said. “Some folks don’t—like the way I live. Now I could say the hell with ‘em, I don’t care if they don’t like it. I do say I don’t care if they don’t like it, right enough—
but I don’t say the hell with ’em, see?”
Dill and I said, “No sir.”
“I try to give ‘em a reason, you see. It helps folks if they can latch onto a reason. When I come to town, which is seldom, if I weave a little and drink out of this sack, folks can say Dolphus Raymond’s in the clutches of whiskey—that’s why he won’t change his ways. He can’t help himself, that’s why he lives the way he does.”