While some 8 month olds might start to drink from cups, it is still a young age for them to do so, so don't be in a rush. A baby's natural way of drinking is to suck and when you take away the teat they do not know how to drink. You can get cups that have teats, then they can be changed to a lid with a soft-like sipper. Also try giving him his bottle, and then give him a cup with juice - he will be content from his bottle and the different drink might make him more curious to try it. Be patient and keep trying - he'll get it eventually.

Try using the ones that have a really soft teat like a bottle. You can get ones that have interchangable teats which help ease into using a sippy cup. Try giving him half a feed with a bottle then put some in the soft teated sippy cup to finish off the feed.

Ive got the same problem with my 8mth old. He will chew the hell out of it, but just wont drink from it. And then he gets very frustrated because he cant get anything out of it. Im thinking about buying a cheap one that isnt spill-proof, so that some drips out, and he knows that hes meant to suck on it.