COCKTAIL. BtVS Intertext/Allusion.
Cocktail was a 1988 Roger Donaldson film starring Tom Cruise as an apprentice bartender. In "Beer Bad" newly hired bartender Xander alludes to it in an exchange with Buffy:
Buffy: You know there's more to it than wiping and kicking. Mixing drinks for instance.
Xander: Well, I've seen Cocktail. I can do the hippy-hippy shake.