Counting by container: một chai nước, một tô phở

Things you don't count one by one, like water, rice or coffee, are counted by what holds them or by a measure: một chai nước (a bottle of water), hai ly cà phê (two glasses of coffee), một ký thịt (a kilo of meat). The container goes where a classifier would: number, container, then the thing. There's no word for "of".

The everyday containers have different names in Saigon and Hà Nội: ly (a glass; in Hà Nội cốc), chén (a small rice bowl; bát), tô (a big bowl, as for phở; also bát) and dĩa (a plate; đĩa, while dĩa in Hà Nội is a fork). The kilo is ký, in Hà Nội cân. Chai (bottle), lon (can), hộp (box) and gói (packet) are the same everywhere.

Once it's clear what's in it, the container can stand alone: Cho em thêm một ly. One more glass, please. When ordering a dish everyone knows, the container is often dropped: Cho em hai phở bò. Two beef phở, please.

To ask how many, use mấy: Anh uống mấy ly? How many glasses are you having?