Freemie cups

I have a set of freemie cups that I hook up to my spectra pump so I can pump while commuting to work and I actually started just using them full time at work since it’s easier than using two sets during the day.

Anyways my question is cleaning them... it says in the instructions not to steam clean them or put in the dishwasher. I just feel like they don’t get that clean with just soap and hot water. Has anyone steam cleaned in the Medela bags (that’s what use with my spectra pump parts)? Or how else do you clean them well? Thanks!