There is a couple FKKs in Munich, but the best known in the region is Colloseum in Augsburg. Do note however, that in Bavaria any unsafe sex is prohibited (including BBBJ). Just yesterday I read an article that claims there are police teams that interrupt sessions to check whether condoms are used. I'm pretty sure the chance of this happening is ridiculously small... and I would be surprised if they'd do it in a big club. Still it means BBBJ are not standard and if possible, girls will ask extra.

What etiquette is concerned, just behave normally. After entering you change into a robe or towel and just do whatever you like (drink, eat, read, sauna, pool). Girls might come up to you, just stay friendly and tell them you're not interested (yet) when they ask to go to a room. If you are interested in someone, you can of course take the first step. Don't spend hours talking to a girl only to decline any further services and if a girl tries instigate kissing, only return the kiss if you want to do more. But honestly, I'm not sure the clubs in Munich are particularly known for public action. For the rest, just relax and have a good time.