This is what I do for my toddler. It's always been a chore to get her to drink water, so I give her a 5:1 mixture of water and juice and we call it juice.  My Ham Grandma gave her straight juice while I was delivering my son. I chastised her, tallying up the calories and explaining that she has been giving her three times her daily need by not watering down her juice. Grandma thought it was funny, Grandpa has type 2. They think it's genetic. They haven't babysat since then.