My son is underage drinking

How can I approach my son about underage drinking and the other stuff he's been doing. Me and my son don't really have a close relationship. He also doesn't have a close relationship with his sister. He's constantly saying he can't stand her and never wants to talk to her. But me and my daughter have a close relationship and it's how I found out about him drinking and other stuff. He's away at college. He's not coming home this summer because his sister moved back home and he doesn't want to be around her. My daughter had gotten on a friend's Facebook that he's friends with to look at his Facebook because he has his set to private and he won't accept his own sister's friend request. He posted a picture where he was out with friends and he had a bottle of vodka in his hand. The picture was from 2 weeks ago. My daughter screenshot it and sent it to me. Hes not gonna be 21 for another 2 months so he's underage drinking. It's not even just the drinking.

When my kids were home for Christmas my daughter found a condom in his room and told me. Me and him had a fight because he should be focusing on getting his college degree not fucking some whore at his school. My daughter also told me he was vaping on Instagram. We've had a fight over that. Last semester he had a girlfriend even though he knows I told him I wanted him to focus on college. He tried to be discreet about it, but my daughter can find out anything. she has a lot of inside sources🤣🤣🤣. She found out and told me and the fight we he stopped talking to me for 2 months and guess what? Him and his girlfriend didn't last. Now I have this new thing to get onto him for. It's just gonna be another fight. I love my son more than anything but my daughter just seems to have her head on straighter than he does. Might be a reason we are so close. Anyway how can I approach this without it being a huge fight? I'm tired of fighting with my kid. I never fight with my daughter but my son drives me up the wall.