"ml bottles" refers to bottles that have a specific volume measurement of milliliters, which is a unit of measurement used for liquids. Full definition
There are two cup holders, a good - sized glove box and door bins big enough to hold a 500 ml bottle of water. (autoexpress.co.uk)
If I take 250 ml of water and pour it into a 500 ml bottle at first, I will think the quantity has changed based on the size of the container. (parentingfromtheheartblog.com)