汽水(qì shuǐ) - fizzy drink in Mandarin

汽水 (qìshuǐ) is "fizzy drink" or "soda", from 汽 (qì), "gas, vapour", and 水 (shuǐ), "water", so the compound literally means "gas water", a fair description of anything carbonated.

It is the general umbrella term rather than a brand name: 可乐 (kělè), "cola", is a specific type of 汽水 (qìshuǐ), in the same way "cola" is a type of "fizzy drink" in English rather than the other way round.

British and American English split here too, and it is worth knowing both translations exist: "fizzy drink" is the everyday British term, "soda" the American one, and 汽水 (qìshuǐ) covers both without distinction.