Hi. I'm a noob but I have worked with and maintained years-old urethane rubber and latex rubber costume appliances. Yes, urethane rubber will stink especially when it starts to degrade due to bacterial growth. That's what you usually get when someone's sweat takes too long to evaporate and bacteria begin to grow. To stifle bacterial blooms, I find a good airing is a necessary first step. A mild disinfectant is okay as long as it doesn't contribute more moisture. To be sure, a thorough blow-drying may be required, followed by a spray paint coating (if this an option) to seal the rubber or foam cells from more moisture. Of course, this also seals in any of the original smells, effectively getting rid of most of it. I've used an acrylic or latex water-based paint to do this. If you wish to find out if a spirits-based paint will do, you may want to test it on a small inconspicuous portion of the costume. I find rubber takes paint well as long as paint used is quite flexible and not prone to cracking or peeling. Good luck!