Do you: wash your feet before class, and anyway, wash them every day? Change socks and shoes every day? Wear shoes that "breathe"? Wear slippers off the mat? Dry your feet well after washing them/showering?
If your feet tend to smell despite all that I'd suspect something like a fungus (aka athletes foot), if that's the case, you need to treat it to get rid of the smell. http://en.wikipedia.org/wiki/Athlete's_foot
Here in Holland I think what you get if you ask at an apotheek is miconazol nitrate to treat it.
Hope that helps.