Disclaimer: I do not own Dragonball Z. For shame.
I didn't do all of the characters... or even anywhere near all of the characters. That would take way too long. But I gave you a good handful of the main ones and some of my select favorites.
Dragonball Z
Goku: A large iced tea, and everything in the pastry window.
Gohan: Green tea latte.
Piccolo: Also green tea latte! Get it? 'Cause he's green? And it's all green? Ha ha ha! Ha...
Vegeta: Starbucks when you could be TRAINING?! Pitiful, Kakarot!
Bulma: Soy latte.
Broly: He'll have a Kakarot cake, please.
Master Roshi: Hot black tea, but he's really just there to look down the hot female cashier's shirt.
Trunks: Probably espresso, but I don't know how many he'd have to order (one for each self, in different times). I don't feel like doing hard math right now.
Videl: Iced chai latte.
Android 18: Double espresso shot mocha. She'd probably get it for free. She'd just have to fix the poor defenseless clerk with her stare glare.
Dabura the Demon King: Who gives a crap? He died early and no one bothered to bring him back.
Hercule: Vanilla soy frap with extra whipped cream. THE CHAMPION gets his post work-out fraps for free!
Krillin: Mocha.
Fat Buu: Lots of pastries! And the clerk!