飲む

How it works

を (object) marks 水みず (water) as the thing being drunk, sitting right before the verb 飲むのむ (drink). The verb stays in its plain dictionary form — no polite ます (polite) — so this is casual. There's no question word か (question); the ？ (?) alone signals a rising tone, the easy “drink some water?” you'd say to a friend.