Florence has more than enough wine bars to keep visitors busy while the explore the city. It's not unusual for Florentines to take a break during the day and enjoy a siesta--a nap or a wine break where you can sit and relax during the middle of the day. Fortunately, you'll find that the city can offer you many spots to check out and enjoy this classic Italian tradition.
You might want to consider checking out Dondino's, a newer spot with plenty of charm and many different wine options served up by some locals who know the wine business like no other. You can also sit outside and enjoy their spectacular view of the Santa Croce church while basking in the fading Tuscan sun.
Another hotspot is Casa del Vino, where the attention to wine is incredibly important. You'll find that each bottle featured is personally looked over and has been carefully chosen. You can sit and relax in their cozy environment and enjoy a glass of red that you won't be likely to forget. Enoteca Pitti Gola e Cantina offers some good choices, as well. The location is also reason to stop by here--the beautiful Pitti Palace is your backdrop while you sip on your choice of wine.