D.M.
hi K....certain sippy cups have a special top to them now days and they now have some that feel and look similar to a bottle nipple.try giving him the sippy but fill it with water soon he will get tired of the water and just not take it anymore.i had to do this with my son.i give him the cup with milk or juice in the mornings and kept it filled with something through the day.then at bedtime he took the cup to bed with water in it.this worked with him but it had to start out with those special nipples for them,and soon it was regular cups,of couse they had to be characters on them..maybe this can work for you too...good luck.