Hi' you could take wire and make in the shape of a cup holder with the design you want, then run the wire up about 3" to 5" to make a loop with and nail it or put a hook in the wood to hang and that way you could take it down to clean.Let me know how you do it, I've working with wood and clay this winter' can't wait to get out side and get my rock garden done.
Thanks - Spider

Using wire is a great idea because then I can take the bottles off too. Just wondering for other projects how one attaches glass to wood. I've seen ideas where they've taken glass bottles and attached them to wood. Is there a drill bit that you can use on glass or some kind of glue that would work? thanks

Hi' did a little checking, you could use a epoxy glue or
a clear silicone glue or you could go to a glass store and see if they have a glue or a drill, but if you have old milk bottles' you wouldn't want to mess them up.When you get it done let me know how it looks, have a good day.
Thanks - Ruthie

Thanks for your research. I'll check our local hardware store for one of these two types of glue. Then I'll let you know what happens.