Making buns
If a child or a parent is near, and you don't want to say 'Dude, I totally had sex with that girl!'. Instead, you say 'Dude, I totally made some buns with that girl last night!'. 'Making buns', putting it simply, is just having sex.
"Omg, did you hear about Demi and Dan? I heard they were up all night making buns last night!"