How do i do this

My son of 4 is refusing to drink water. He will drink sugary beverages like tea lemonade but will not drink water. I've seen him go all day with only taking a few sips of water. I'm afraid he'll get sick of he does this, but I know giving into him is much worse. We have taken all sugary drinks out of the house and the only things here to drink is water and milk... What should I do?