In the heart of the historic center of the city there are lots of these bucchette del vino, or wine windows embedded into the walls of buildings you pass on the sidewalks. They were built in the medieval age of the citta, allowing passersby to purchase a glass of wine as they walked by.
Some of them are operational again.
I spied a wine transaction going on recently and stopped to film it. First you ring the bell over the window to show your interest. Someone on the other side will great you, ready to offer you a selection of red, white, or rose wine, typically tailored to the season (it is Italy after all!). You pay, and presto! you are given your wine! That’s all there is to it to enjoy a Florentine tradition that dates back 700 years or more.