I've been trying a technique lately in an effort to recycle, wherein after juicing a bunch of citrus, I'll take the spent shells and pour some inexpensive spirit over them in a Mason jar. I'll let this stand for a while, infuse a bit, then strain off to produce a slightly bitter cordial. It's a simple, cheap way to wring a little more flavor out of what would otherwise be waste.
The result is also an easy way to put a twist on an otherwise basic cocktail. Like this one, which became a straightforward response to an unspecified request for "just a drink" (in which case you're getting whatever I have to use up). It was named (terribly) for its various citrus content, combined with a self-referential pun. Fucking meta, man.
2 oz grapefruit-infused white rum
3/4 oz lemon/orange syrup
1/2 oz lime juice
Shake and strain over a fresh large ice cube. Hurl disdainfully at the freeloader who begged it from you. (Or, like, drink it.)