I didn’t figure out I was nonbinary and asexual until my mid twenties. I had an entire gender crisis in high school too. But at the time I didn’t know either were things you could be so I’d just concluded that I was cis, but that I was deeply uncomfortable with the expectations society puts on boys/men.
Sexuality was an even wilder journey. Not only did I initially think I was heterosexual but I was outright homophobic. Turned out to be that I was mistaking being uncomfortable at overt sexual advances as dislike of gay people. I didn’t have the same problem with women because “of course I like girls, I just haven’t found The One™©® yet” lol. Then when I finally thought about it more I realized that I didn’t really feel any differently about men and women so I must be bi. Finally I eventually realized “Yeah dumbass, 0 = 0. Good job.”
If I had to guess I’d say either sensory issues with drinking alcohol itself, or the fact that drinking is another one of those social things that many only do because “it’s what people do”
In my case it’s a sensory thing but I also apparently have that gene that that makes you really sensitive to bitter. So even the fruitiest “you can’t even taste the alcohol” drink tastes to me like paint thinner smells.