Osteria al Ponte is one of the best bars in Venice, located close to Basilica dei Santi Giovanni e Paolo.
In Venice, it's pretty popular to go to these types of bars, also called bacari. A 'cicchetto' is like a small appetizer, you can get as much as you like, and they range from €3 to €5 a piece. It's usually enjoyed with either a glass of wine or Spritz (super popular and cheap in Venice).
Osteria al Ponte is one of my favourites and would highly recommend a visit here. You can also include it in a 'bacaro tour', so you visit a few bars during the day and get a cicchetto and a spritz.
Recommendation: try Select Spritz, which is typical Venetian. Aperol was born in Padua, a nearby city, but Select was born in Venice, and it's a must here. The one in Osteria al Ponte is pretty good (even though I still prefer Aperol).