My daughter would only chew on the Nuby cups too, and not really drink from them. But not enough teeth yet to chew through. I bought the cheapest hard tipped sippy cup from Target (I think it was the munchkin brand and was 99 cents), and took the valve out. She quickly learned that she could get milk/water out, but we did have her on a bottle for morning and night feedings. After a few days, we stopped the bottle, and she was only on a sippy cup with the valve out. It made more of a mess, and we had to teach her not to drop it, but she learned that something does come out (rather than all of the stress of trying to suck too hard and then refusing to try). Now that she has the hang of it, we put the valves back in, and she knows exactly what to do (and it's so much less mess!).
A friend of mine had me try the 'take and toss' cups, and they work well too (and you don't have to toss them). No valve, but doesn't spill. I found it easier to drink from myself than some of the other sippy varieties with a valve. The only thing I don't like about them is that they have a snap on lid, which has the potential of coming off to easily if dropped.