A girl drink usually has a name like "Some kind of fruit + tini," anything with "Breeze" or "Sunrise" in the title, and/or containing some kind of sexual innuendo: "Against a Wall" or "On the Beach." Also, they look like something Rainbow Brite and her crew would drink on a bender, and they usually have more accessories than Mr. T.
"Dude, what is that girl drink in your hand?"
"It's an apple-tini, easy on the 'tini'"
"I'll have a Guiness, and a gay beer for my gay friend"