Have your water bottle filled with water free of charge in many cafés, bars or shops in Berlin. Wherever you see a refill sticker, you can get drinking water for free. The refill spots thus support the zero waste principle and want to help other people.
Drinking fountain of Berliner Wasserbetriebe
You can also find free drinking fountains from Berliner Wasserbetriebe at many public places in Berlin. These are directly connected to the Berlin drinking water network.
So always take a water bottle with you on your Berlin trip, drink enough and travel sustainably.