Go for an Aperitivo
The Aperitivo is a tradition all over Italy. From around 6pm people gather to have a drink together, usually served alongside nibbles or finger food of some kind. The slightly bitter orange Aperol Spritz (aperol and prosecco) comes from the Veneto region, Padua to be precise; so, it is the local aperitivo drink of choice.
You could also go to one of the antique taverns or wine bars called baccari for a small glass of wine called an Ombra (shadow) and cicchetti which are a kind of Venetian tapas, usually seafood based.
It is said that there are more Osterie and Baccari than Churches in Venice, so you should not leave Venice without visiting one of them.