"Drink clear water."
Translation:맑은 물을 드세요.
드시다 - honorific form of both base verbs:
마시다 (to drink) and 먹다 * (to eat) (먹다 has another honorific form, 잡수시다).
드시다 is believed to come from 드다 (of which one of the meanings is 'make part of').
Using with food and beverages, 드시다 literally means 'please, accept this as part of yourself'.
In English (as many previous posts have pointed out), it is the equivalent of "taste, relish, savor, enjoy" etc.
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