To truly experience the essence of Budapest, you shouldn't miss out on visiting the city's famous ruin bars. These are quirky, fun bars and cafés located in abandoned, old or ruined buildings. They have mismatched furniture mostly from yard sales or antique shops, random decorations and a very unique atmosphere.
Ruin bars are not only places for drinks: they are institutions! Many of them organize live concert, exhibitions, farmer's markets, beer or wine tastings, flea markets, craft fairs, open-air cinema screenings and various events that are not only appealing for the tourists but also for locals. Basically, they have something to offer for everyone. They are perfect melting pots of fun, entertainment, underground culture and gastronomy.
I highly recommend you visiting them during the evening AND also during the day as they have incredibly different vibes. During the day, they are great places for grabbing a cup of coffee or a light meal, a few people are even sitting there with their laptops, doing work! During the evening, the ruin bars become more and more lively, people start to have drinks and as the night progresses, many of these bars turn into clubs where you can dance the night away.