Know what you're going through, I just weaned my 2.2 year old a couple of months ago, and it was frustrating as he would resist drinking any of the milk. We found out that since he use to take his bottle in bed or in our arms, he doesn't mind taking the sippy cups in those positions, so that's how he's taking his milk now (contrary to how the book said that baby would relish the freedom of running around with the sippy cup in hand
).
If you are worried about his milk consumption being down, as long as you are giving him other forms of calcium it should not be a big concern, ie yoghurts & cheeses, etc., it will take time some time before baby will adapt, but eventually they will get there, in the meantime just be patient and try to find what can work for you and baby best. Good Luck.