Was recently gifted a decently large collection of growlers from a friend moving to a state with growler laws even less friendly than California's. As most of these are from breweries I'll actually visit, if its cost effective enough I'd like to clean them and get some use rather than donate them to city recycling. Unfortunately a decent number of them have what appears to be accumulated left over beer funk/build up. I dont get a mold smell out of any of them, but there is a noticeable ring or junk internally around the bases. Is there any way to effectively clean them such that they could be reused, or should i just write it off as a lost cause? To clarify, they are 2l swing top growlers. If this is the entirely wrong forum to ask this, I apologize, but y'all seem to be the sanitation experts.