Does drunken fighting have any basis in reality?
I don’t think this is the question you’re asking, but, yeah, bar fights are a thing. People will do all kinds of stupid things while boozed up, as any bouncer or bartender can tell you.
I seriously encourage you look for work stories from bartenders and/or bouncers. They make for some very amusing reading, and can be very useful inspiration when you’re writing someone who’s been killing their brain cells for the past four hours.
Drunken patrons are mostly harmless. Most of them haven’t been in a fight since high school, and don’t know what they’re doing sober, to say nothing of when they’re unable to walk in a straight line. Mostly.
There are plenty of unfortunate accidents, or fluke occurrences, where a bar fight turns fatal. They’re the exception rather than the rule. But it is there.
There’s also plenty of unfortunate incidents where someone tried to run down the person who pissed them off, when they’re staggering out of the bar, or someone pulled a knife or gun.
But, I don’t think that’s what you wanted to hear about.
There are (at least) a couple Chinese martial arts variants that imitate drunken movements into their combat style. One is Drunken Monkey Style, which is, unsurprisingly, a variant of Monkey Style Kung Fu. The second is Drunken Fist, which is a variant of Shaolin. There’s also a Wushu Drunken Form, which is what you may have seen Jackie Chan practice on film. (At least, I think that’s the variant he’s using.) There may be others I’m unaware of.
The important thing to remember is that the practitioner behaves as if they are drunk, they don’t actually get wasted. In both cases, the martial artist uses exaggerated and relaxed movements to mask their movements, and make it more difficult for their opponent to read their body and react. There may be other benefits involving resisting restraint holds and taking hits, but I’m not an expert on these styles, so I’m not 100% certain what the full implications are.
There are real applications here when dealing with a trained opponent. There are also practical reasons you might want a foe to think you’re drunk until it’s too late to respond. Which goes beyond the scope of these martial arts.
So, if you’re asking, “is there a school of Kung Fu where you get drunk, and fight people?” No. There isn’t. However, there are multiple Chinese styles where you pretend to be drunk to confuse and distract your opponent; as tactics go, it’s not a bad one.