If you're asking about play docs and their equipment, I'd say that in general most play docs that I know are pretty conscientious. Any reliable play doc would be happy to discuss this issue with you before your first play date. Additionally, I'd add that most infections resulting from play involve carelessness, such as becoming distracted and allowing something that has been in the rectum to come into contact with the vagina or using household objects for urethral play.
For home play, the most practical and therefore probably best method of cleaning stainless steel is a very thorough wash using dish detergent, a brush and plenty of hot sudsy water, followed by a thorough rinse and then foil wrapping and baking in an oven at 350° for an hour. Simple, easy and reliable as long as the instrument remains in the original wrapping and is used shortly after cooling to prevent subsequent contamination. This yields SS implements that are sterile (free of all viable bacteria, spores, viruses and other pathogens).
The gold standard for play doc use would be be a pressure cooker with a 15 lb. pressure valve running for at least half hour with everything being left in the cooker to cool and remaining there until used. This method, however, can be degraded by carelessness such as improper loading of the pressure cooker or inattention to other details.
Instruments at a hospital are often autoclaved. An autoclave is just a big pressure cooker running at higher pressures (and therefor higher steam temperatures) than a pressure cooker at home, which means that the sterilization cycle is therefore shorter, but not necessarily more complete. It should be noted that Sterile is an absolute standard (NO viable pathogens).
Typically the only reusable stainless steel instruments in med play that absolutely have to be sterile are sounds. The rest can be cleaned thoroughly and then soaked in a commercial, high level disinfectant, designed specifically for disinfection of reusable medical equipment that can't be autoclaved, such as endoscopes and reusable rubber products. It should be noted here that there is NO WAY to sterilize anything by soaking it in anything, including Alcohol and / or bleach). Fortunately most or all of this sort of med play paraphernalia is prepackaged, single use sterile equipment (such as needles, cutting edges, etc.). Interestingly, specula can be simply disinfected and need not actually be sterile; but, why not sterilize them too, while you're at it with the sounds.
Finally, YOU CANNOT STERILIZE INSTRUMENTS BY BOILING THEM, although, you can disinfect them in that manner, which is a lower standard.
Feel free to contact me if you have questions.