R.S.
I have 4 children and have introduced the sippy cup at 6 months for all of them. I put a mix of water and juice, 2 ounces of Gerber juice and 2 ounces of water.
You are going to have to be very patient. In the beginning they don't get anything out of it. It is mainly to introduce the new item. They will chew on the spout, etc.
I would even suck just enought to get some juice right at the very tip, then put it in their mouth. Just to kind of let them know there is something good inside. When they were ready to actually drink out of it, that really helped. I do have to say that it can take anywhere from 1-3 months to really get it.
I would suggest the avent sippy cup. That was a good one for my son this time around, he had a little more trouble then the others.
After all of my children have mastered the sippy(around 8-9 months old), I only gave the sippy cups. They had no need for a bottle and didn't even miss it. Believe me it is WAY better this way. My friend's children were all hooked on the bottle. It is so hard to take it away once that happens.
Good Luck!!