Yes I know, it may sound a little ridiculous but I want to know because I need an answer.
If we believe Asterion is telling the truth during the drinking game in Chapter 17, he has never fucked a guy (the question includes the caveat "without using a charm", but I'm pretty sure he has never had a charm), nor has he sucked a dick.
Now, there are some general implications about Asterion and Phroneos in the backstory vignettes, but as far as I know we don't know exactly what happened. That could have stayed platonic.
(Strictly speaking, we also don't know anything about any potential relationships with women.)
I kind of got the impression that Asterion was fairly young (early teens, perhaps) when King Minos sent him to Daedalus's labyrinth, though that doesn't necessarily preclude anything... as pointed out above if we assume he isn't lying during the drinking game he seems to have not done anything physical, but there are times where it seems like he's playing dumb when the topic of sex comes up so who knows?
in life he didn't have many chances. he was exiled and died young. in hades, who knows if that's even possible on the afterlife. in the hotel there's a bunch of rules restricting him, unless some particularly nasty master thought of that sort of thing as punishment. probably not, we'd have hints that happened if the story wanted to go there. so i guess there's a decent chance he'd be a virgin, which is the worst punishment of all. be undead for millenia without getting any action is too cruel. can't believe our moo is an incel, maybe.
I think is better to keep a virgin, that to think about the big number of sexual punishment or torture that we humans already created. Its wared to be confident to assume, if that was the case, he will sabe some big problem's with erection, cause flashbacks and shit, anxiety, and erection disfuncion due to stress. Also, RIP his ass.