"I drink water."
Translation:Jeg drikker vann.
'drikk'(drink) is the imperative of 'å drikke'(to drink). These are usually commands.
Drink the juice! Drikk juicen/jusen!
'drikke'(drink) is part of the infinitive 'å drikke'(to drink). These may appear after modal verbs, such as 'kan', 'vil', 'må', &c...
Can you drink the milk? Kan du drikke melken?
'drikker'(drink(s)) is the present tense of 'å drikke'(to drink)
He drinks OR He is drinking. Han drikker.