How to celebrate stag party in Berlin?

Looking for ideas for a stag party in Berlin, I want something unusual and fun, not a banal bar or club. We will be 6−8 people, we want to have fun, so that then there was something to remember. Who has tried or heard what, share options?

You can gather your friends and rent a beer bike – there is such a thing in Berlin, you ride around the city, drink beer, chat, music plays. The format is not standard at all, it fits just for such events as a stag party. The atmosphere is super friendly and fun. Look here, there is all the information: berlinbeerbike.eu

Is it all rides around the city center or can you choose your own route? And I wonder if you can get your own drink there or only what they have?