Running water, free restrooms for men and women. It's a bit noisy and doesn't feel very private, but it provides relief in the middle of the city, where there aren't many free places.
In the summer for 12 weeks there is the Rheingau wine well here. There are 3 wine growers represented and you can buy delicious wine. As in Munich beer gardens you can bring your own food and buy only the drinks. You do not always find a "own" table, but there are always great conversations with many people if you put yourself somewhere. It's always good mood.
Also on Rüdesheimer Platz you will still find a so-called 'Cafe Octagon', one of about 30 existing in Berlin historic need institutions. This one has been remodeled and has normal toilet bowls for both man and woman.