Happened to see a post by UnderEst in the Travel Health & Fitness thread; the Marriott part is below. Thought I'd give a heads up in case anyone wanted to use the sauna (the post was part of a thread about nudity in German spas).
"I recently used the sauna at the Munich Marriott Hotel and they had an English placard placed next to the door on the sauna that clearly stated swimsuits and any garments other than a towel are not allowed in the sauna."
Cheers.