When my SD was a baby, she was giving un-watered down juice and her baby teeth rotted and she had to have major dental work. She also is addicted to sweets.
For years she would suck down juice like it was going out of style. Glass after glass, after glass. She wouldn't drink water or anything that wasn't strongly flavored or sugared down. Milk only if it was flavored with strawberry or chocolate (and of course sugar).
My husband finally saw the light and we started pushing drinking water more often. She would beg for juice. She would cry. She'd refuse to drink water because it "had no flavor."
We started watering down the juice. First maybe about 10%, then maybe 25% and gradually more and more until we got 50% juice and 50% water. Then, and only then, did we break her of the juice habit and she started drinking water. It took at least a year.
Now she drinks lots of water and she can have a glass of unwatered down juice a day, but usually just drinks water. She will drink milk occasionally. We broke her of the begging for pop, she can drink it on special occasions.
High fructose corn syrup was the culprit, it was hard to break her of that addiction. We now buy juice that does not have it in it and we've found it's not addicting. I think it also took time for her taste buds to adapt to something less strongly flavored.
I think watering down juice or limiting it is a GREAT idea.