N.H.
My daughter will drink it... I get the Parent's Choice brand from Wal-mart. I always give it to her really cold without mixing it in anything. There are 3 different flavors and she likes them all. Before she had these, we always put liquid vitamin drops in her milk and it changed the taste and smell. It seemed terrible to me but she loved it. Why not try the milk and vitamins to see if she will drink that, then perhaps trying to mix or add some chocolate syrup to it for a few days then switch?
My daughter has always been small and the Dr will always comment on it, but I was told that it wasn't until she was under weight would we need to deal with it. I know some people will consider being in the 5% or 10% underweight, but my Dr considers it to be off the charts to be underweight. She's almost 2 yrs old now and 23 lbs... At 18 months old she was 21 lbs. She's just very active and it doesn't seem to help feeding her higher fat foods or these drinks. Have you thought of getting a second opinion from another Dr? My pediatrician doesn't push the issue as long as she keeps gaining and stays on the chart.