When rarely had juice in the house until I was pg with DS. Then juice was just about the only thing that I could keep down in the morning, so we (DD and I) got in the habit of having juice with breakfast. Now it is totally part of the breakfast routine to have a cup of (watered down for the kids) juice in the morning, but that is it for the day. They know that it is only for breakfast, and don't bug me (very often) for it at other times. We brush after, their teeth seem to be doing fine, and they are both string beans so I am not to worried about the extra calories.
DSS biggest by far
DD littler
DS littlest