What does eating and drinking do?

Drinking and eating in Watch Dogs 2 doesn't bring anything to the game. It won't affect your character, nor it will affect the gameplay of the game. So you can just keep eating and drinking as much as you want, or just totally ignore it.

There was some purpose for it in the first game. Drinking soft drinks for instance would heal you and regenerate your focus meter. But it was not kept for the second game.

From this thread, it looks like they're just aesthetic and don't really have an impact on you.

Yeah, I tested it out at a bar and for 5 minutes I just kept drinking beer, must of drank at least 30... nothing happened. Its cool they threw it in, but its just weird that it has NO purpose considering how many locations there are, and they show up on your map like they mean something.

It's worth noting that in this thread, its indicated that eating and drinking used to play a role in the original Watch_Dogs, but don't anymore.

Well the purpose of there being drinks in the first game like energy drinks, coffee, etc. was to fill aiden's focus meter. Marcus doesn't have that any more.