I use hydrogen peroxide and plain natural soaps (kirk's, dr. bronner's, etc.), wash well, and hang up in the shower to drip dry.
please don't use fleet or similar vinyl products. you are just putting way more toxins -- and way more dangerous carcinogenic toxins -- into your body than you are taking out. I had an old fleet bag that I boiled and cleaned for days and then it lasted me a few years, but then it got a leak and I stupidly threw it out. the newer ones have some different composition, and when I tried boiling that one the hose turned all soft and blue colored and still has a vinyl smell. they are really, really toxic, just please avoid the vinyls altogether.