I went to walmart in search of a plastic slinky to see if the girls like to play with them. Let me tell you, the toy dept doesn’t have anything like a slinky. I couldn’t find one. So I went into the baby dept to try to find some plastic keys for them. I found some, but they were big, bulky and had strange characters on them. I couldn’t see them fitting them in their mouths, but I found this package of Bright Starts Lots of Links (24 pack) for 3.96. They are the links that you click together to hang toys off of for mobiles, or you can make a full circle out of them. They are thin enough for rabbits to pick up, and are the same hard plastic as baby key rings. And when you link a few of them together, you can shake one end and they make a plastic rattle noise from the links hitting each other. Here’s a photo of them I found


So if your rabbits are into plastic toys like this and slinky’s, they’ll love them. What’s also great about them is you can link them to hang from the ceiling of the cage. Or there are tons of them to split up if you have more than one cage.
I just got home and gave a few linked up to Hailey who’s in the play area. I shook it and she came running up to it to check it out. I guess she really liked the sound. She’s smelled it and put one of them in her mouth, but hopped off to do other things. Either she needs more time to check it out or she doesn’t like plastic toys. This is her first time with a plastic toy, so maybe she’ll come around.
So my test is a dud so far, but your rabbits might like them. It’s cheap and definitely worth a try! 
OH….and I got these from walmart for 3.49. I keep looking on the internet and they are selling really expensive for other sites…weird! So I recommend checking out walmart first in the baby teething ring area.