okay here are some ideas:

They are named Carbonpups, a mix of the words carbonation and puppy.
They mostly have carbonated drinks inside of them, but on rare occasions they can be filled with some other type of drink. Their shells may look hard, but they're actually kinda soft, it's pretty much skin but smoother. They act pretty much like normal dogs, just a little more cautious than most.
That's all I have for now.