Formal:
* Avez-vous acheté quelque chose? (Have you bought something?)
* Avez-vous fait des achats? (Have you made any purchases?)
Informal:
* Tu as acheté quelque chose? (Did you buy anything?)
* T'as acheté quelque chose? (Informal slang, literally "You have bought something?")
More specific:
* As-tu acheté des souvenirs? (Did you buy any souvenirs?)
* As-tu acheté des vêtements? (Did you buy any clothes?)
Note: The "vous" form (formal) is used for addressing someone you don't know well, someone older than you, or someone in a position of authority. The "tu" form (informal) is used for addressing someone you know well, someone younger than you, or someone of equal status.