The sauna world of the Aquaworld resort (http://www.aqua-world.hu/en/aquaworld/saunaworld ) is open to naturists
from 16:30 until closing time each Thursday and Friday as well as every other Tuesday (from 16 October). Tickets for sauna world only are available.
At one of the sauna cabins, various sessions (salt, tomatoes, ice, honey, etc.) are available (+500 HUF/person/session). Check the sauna programme here: http://szaunaszeansz.hu/szaunaszeanszok-az-aquaworldben.html (Hungarian only, and you may want to register for the sessions to be sure to get in).