I found this list of cocktails with dirty names, so I decided to make a list of which each of the marauders era characters would order and the circumstances as well.
James: Tie me to the bedpost. He orders it to flirt with Lily. When he falls in love with Regulus, he tries the same thing but Reggie remembers and gets offended that he's trying to use the same line on him.
Sirius: Pornstar martini. That's his favourite order ( because of the name); he walks right up to the bar, poses suggestively and basically moans that order.
Peter: Blow job shot. His friends always turn it into a joke and he has to endure a good ten minutes of mocking. Peter really likes them so it's still worth it.
Remus: Ass candy. Orders it while looking at Sirius and flirting, but when the orders out, he has to look at the bartender to take it and he gets super awkward. Turns tomato red and can't say a complete sentence embarrassed.
Regulus: F'ckn werther martini. His friends said he had to order a dirty drink. He picked this thinking he'd outwit them so they couldn't make jokes about it. Sadly, they adore to make a big embarrassing deal of him swearing (even though he does it regularly) so that did not work.
Barty: Not your man's balls. He orders it very loudly while staring into Regulus's soul and then proceeds to force him to drink it.
Evan: The stiffy. Barty makes a joke about how he could give him one of those for free, every time!
Marlene: Drunken milf. She always accompagny it with a joke about sleeping with James’s mom.
Dorcas: Slow screw. Orders it after Marlene orders her, cause it's the only way to go with milfs.
Pandora: Hot lesbian sex. She orders it as her way of coming out, but she didn't like it, so it's Barty who ended up drinking it and commenting on how delicious lesbians were all night.
Lily: Shameless tart. It's her party drink, so when she orders it, her friends know they are in for a great night and that they will get shitfaced.
Mary: Reconstituted VERgin. Orders it during a dry phase, complaining that it's been so long since the last time she had sex that her virginity was growing back.
Snape: Adios motherfucker drink. It's his exit drink of the night, cause Lily would convince him to come, then the idiots would get on his nerves, but he can't leave without having at least one drink.