Is to closed up? Bottles generally start to smell after a while. Even my Yeti cup (with lid) felt like it needed to be washed occasionally… not every day, but I don’t think I went a year. I’ll typically use normal glasses around the house and after using them for a few days they start getting cloudy. I don’t think it’ll make me sick, but if anyone were to see it, I’m sure it would look gross, so I change them out when I notice.