"¿Ya compraron ustedes los vinos?"
Translation:Did you guys already buy the wines?
'Wine' is the same singular and plural in English if referring to an unspecified wine - a glass of wine, two glasses of wine, ten bottles of wine. If you are specifying a wine you may say - I bought two different French wines; Unspecified - I bought two bottles of French wine.
For this sentence, I think both wine and wines should be accepted. Wine can be either uncountable as in your examples or countable.
"did you already buy the wine" should work, add duo. "wines" is not correct. Have some common sense
I thought 'ustedes' was a formal form of address - 'guys' sounds far too informal!