I've been going to FKKs for years, sadly they are no longer what they used to be pre-COVID. Used to be you would get max 50€ for 30mins even at the best clubs and they were packed with girls.
Now it's standard 100€ for 30mins and most will push hard to upsell you. There are also less girls around. If you do go my advise is to stick to Sharks near Frankfurt airport. It has the best selection. There are some German forums were you can read reviews on the girls plus a handy map of where they sit in the club. Just avoid Messe times.
Thanks
I wonder how legit this site it, the girl looks amazing
Alternatively you can try Kaufmich for Indy action.