水割 みずわ
mizuwari

Noun
no-Adjective

1. cutting an alcoholic beverage (usu. whisky or shōchū); diluting an alcoholic beverage; cut drink; diluted drink; watered-down drink

水割 みずわりをもう一杯 いっぱいください。
mizuwario mō ippai kudasai.
Another Scotch and water, please.