T.T.
To introduce my kids to the sippy cup I never replaced the breast/bottle with the cup. Instead, I made it part of their solids meal. At first I held it for them until they actually got the hang of it, and then they held it themselves. Don't make a big deal of it, just incorporate it into the meal as if it's always been there.
I would mix up the liquids in the cup so he doesn't associate juice with the cup. Just make it a regular part of the meal and he will get the hang of it.
I would also take it out with you on shopping trips, etc. Only give him liquids in the cup when you are out (no bottle) so that he gets used to that also.
It does take a little time, but he will get used to it. I breastfed both my babies (supplemented w/bottle w/first) and my older son was off the bottle by 9 months and my younger by 10 months. I would think that if your son is not too attached to the bottle he will get the hang of it quickly also!!
Good luck!!