There are no drugs that can change your sexual orientation. This includes alcohol.
Science has shown that most people's orientation is actually a shade of bisexual. Religion over the centuries has directly and indirectly forced everyone to believe 100% heterosexuality is the norm.
So for a lot of people, they have conditioned themselves to suppress any homosexual urges.
There's a part of your brain that operates on instinct and a part of your brain that works on determination.
Imagine you have your favourite cake in the fridge. Your instinctive brain is saying "fuck yeah, let's go to town", your thinking brain says "don't eat it, you're on a diet".
So when you haven't eaten in a while or your inhibitions are down chemically, you're more likely to let the instinctive brain tell the thinking brain to shut the fuck up and sit in the back seat.