bkr water bottles aren't intended for boiling hot liquid (or for freezing) and we don't recommend putting hot liquid in unless the glass itself is already warm. The glass is not tempered so you'll want to avoid rapid temperature changes which could cause your bkr to crack.     Bkr cups are temperature shock resistant. You can put boiling water in them followed immediately by ice cold water and they will be perfectly fine. Please don’t freeze your cups with liquid in them (or any glass for that matter).