Hi Bubble
here's a list of Hotels on the Black Sea Coast that specialise in Spa's and mineral treatments:
[url:u5cy11x5]http:
//www.
questbg.
com/en/lifestyle/life/1020-the-black-sea-coasts-best-spa-hotels[/url:u5cy11x5]
However, this will help with treatments, but not so much the 'natural' spa's.
The best 'Spa Town' is Velingrad, but this is across in the Rhodope Mountains and probably too far a hike from Sunny Beach:
[url:u5cy11x5]http:
//www.
questbg.
com/en/area-focus/rural-a-authentic/571-therapeutic-velingrad-bulgarias-best-spa-town[/url:u5cy11x5]