Izakaya, pub type restaurant is a very popular place to dine and Izakaya restaurants are everywhere but it is a custom to order a food there. If you are not hungry or just want to have a beer on your way back to hotel or after the dinner, Izakaya is not a correct place to enter.
Therefore bar is better place to visit and ordering food is basically not a custom there. Of course there are cozy bars, which are located on the skyscrapers and offer expensive cocktails and magnificient views, but there are also many bars which you can enjoy cheaply during your stay in Japan.
They offer craft beers from the local microbreweries in Japan and sake, shochu and other alcohols. Then, you can easily meet local people and enjoy the evening there. However, these bars not so easy to find. May be no prices listed outside. Just before entering the bar, look carefully the neighborhood. Better to stay away if it is located at the red light district to avoid being overcharged!