What you order on a date can definitely send a signal, whether or not it's one you're conscious of. Sure, the list below is mainly full of generalizations, but there's some truth to every stereotype...
Martini: If you're a guy, you're trying to impress (and it's probably working). If you're a girl drinking a dirty martini, you're a hot mess: the dirtier, the messier, the hotter.
Vodka on the Rocks: Too self-conscious to actually order a martini.
White Russian: Obsessed with The Big Lebowski, and probably The Daily Show. Or, you just like to drink dessert.
Bud Light: You're easy going, laid back, and at home at a sports bar. If you're a girl, you know how to hang with the guys.
Stella Artois: You have no particular knowledge or affinity towards beer so you just order "Stella" cause it's familiar.
Lillet/Campari/Aperol: You're twee, and possibly like to throw around words like "mixology."
Vodka Cranberry: When in doubt, you stick to what you drank in college.
White wine: You're definitely a woman. You're possibly a little uptight.
Prosecco: You're often a little uptight, but tonight you're looking to party.
Whiskey, neat: You're hot. Regardless of gender.
Jäger: Secretly wishing you were hanging out with your buddies.
Vodka Gimlet: You're a huge dork, but you hope sort of in a cool way?