Upvote:3
A good starting point might be Jochen Schweizer (website in German, no affiliation). They sell vouchers for experiences which includes bungee jumping, tandem jumps, ice-climbing and a lot more.
Have a look at the website (with a translation tool). On the left there is a search bar where you can filter for Price, target group ("FΓΌr alle"), category and location ("Ort"). Filter for Adventure&Sports ("Abenteuer & Sport"), some of that might be adventurous enough for your liking (I doubt you were looking for a golf experience).
If I understand their business model correctly they sell a voucher for an experience and then you have to agree on a date with the local guide/organizer (which could be variable also in function of weather conditions, you can't do outdoor ice climbing in August), so make sure this fits your plans before you book. At least it can serve you as an inspiration for further internet search.