Hey Diane,
The drink bags you are talking about, or at least the ones I think you are talking about are bevi bags http://www.bevibags.com They were featured on the abc's Good Morning show a while back too http://abclocal.go.com/wabc/media?id=5901849 They are a good alternative to standard commercially available juice boxes or drink bags as you can put more natural drinks in them, but if you are looking to just switch away from bottles and sippy cups there are more practical cups with straws that I could talk to you about that will help encourage straw drinking. There are also some cups I can recommend if you are looking to start open cup drinking with him. Let me know off line and we can talk.
~ Christine Horvath, MS, OTR/L