Most folks will already have a reusable water bottle on them. Restaurants are happy to fill them for you, that way they also don’t have to dump out un-consumed water and then wash the glass. I have taken my water bottle into venues and other businesses there for years!
Also, if your water has gotten warm and you are about to empty a bottle so you can refill it with cold water , please empty it into a potted plant or on a tree and they will be happy too! They don’t care if it isn’t cold.