I've encountered a measuring cup which has units of カップ, 水mℓ (水ml), 米[unknown kanji]g and [three unknown kanji]g. 1 カップ corresponds exactly to 200 水mℓ.
According to Wikipedia, there's a Japanese cup that corresponds to 200 ml. By contrast, the US customary cup is approximately 237 mL, and an imperial cup (as in the British empire) is 284 millilitres.
How did Japanese obtain a unit of measure called a カップ which corresponds to neither the British or US unit of measurement?
This post on cooking.SE is about 合, which is 180 mL.