I've tried almost everything with limited success, before I came up with a process that works for me. I hand wash the dirt, grass, etc. off my VFFs with a mild soap and warm water, then I clip them to a coat hanger with a couple of clothespins, toes pointed down, hang them in the shower, and pour a half a cup of listerine into each shoe. I leave them there overnight to drip dry and the "funk" is gone come morning.