My eighteen month old categorically refuses to drink milk from a cup. She'll only drink it from a bottle. We've tried free flow beakers, munchkin 360 cups, a doidy cup, different straw bottles. No matter why type of cup we use, she will not drink her milk. She will gladly drink water from any of these cups. We've put the bottles away from the around ten days ago and she is still refusing milk. Any advice?