Sun Therapy
Getting out in the sun is important, but it's not a catch-all treatment. However, the concept of sunlight therapy was used in illnesses from depression to tuberculosis. Football and soccer players were especially big proponents of the treatment, but it was given to almost every patient a few decades ago.
Shower Hood
The shower hood was something no one needed but was created anyway. Marketed toward women, this hood promised to keep makeup and hair intact while getting your body clean! It was a huge failure long term though because as it turns out, women also like washing their hair and face.