If you are at a party and all of your friends have hooked up with someone and it's just you and one of your friend's fuck friend's bros/girlfriends/what-ever-the-fuck-people-call-friends-nowadays.
Anyway, if it's down to just you and them and you friends need them out the way to have a good night, a sacrifice fuck is when you give up yourself for the good of your friends.
Donna: Betty, Megan and Emily had all hooked up.
Donna: Yea, but, I was all alone and the guys they were with had this loser friend with them who kept saying "bros b4 hoes
", and "let's go man these hoes are prudes
Kera: So whaddya do.
Donna: I sacrifice fucked him in a back alley so the girls could enjoy their boy toys for the nite.
Kera: You are a true friend.