"Drink clear water."
Translation:맑은 물을 드세요.
마신다 is a correct answer. 드세요 is a formal word for 먹다 (yes Koreans do say "eat liquid")
Polite way of saying "Please try/enjoy/treat yourself with "something one can drink or eat" = "something" + 드세요
You can use for both drinking and eating.
피자 드세요 = Please try pizza/enjoy pizza
콜라 드세요 = Please drink/enjoy/treat yourself with coke
햄버거 드세요 = Please enjoy/try hamburger
사이다 드세요 = Please drink/enjoy/treat yourself with soda/7 UP