I have 2 glass bottles, a 20oz & a 34oz. They are gorgeous to look at but they are impossible to clean properly. Some of the drink tablets leave a colored residue on the inside of the bottle that is nearly impossible to get oft due to the bottle shape. I've emailed the company and was suggested to use rice or coarse salt inside the bottle to scrub it, doesn't work. The other suggestion was for me to buy their bottle brush. Clever marketing ploy by the company. The caps are impossible to get properly clean as well, I was using my 34 oz bottle daily and a good rinse before bed was good for it until I used one of the residue causing tablets. The inside of my bottle is stained orange now. I left my lid and bottle on my counter, open while I was away for the weekend, and now there's black stuff growing at the bottom of the bottle and I can't get it off, also its on the inside of the lid where you cannot get any kind of cloth or sponge to clean it off. The "insulation sleeve" is a joke, it doesn't keep the water any colder for any longer than not using it. Tossing these bottles and I'm going to go back to my Owala Freesip. I will say that I do like the flavor tablets, so that's a plus. The photos I've included arr of the black stuff growing in the lid and inside the bottom of my bottle and of the staining on the inside of my bottle.