Here are 3 coasters from Just Funky.
The photo was discovered at a trade show maybe 2 years ago or so, and then the coasters never seemed to come out / go for sale anywhere. You can see they're made of some kind of laminated/shiny top hard board substance. They're all to be classic style & the Tails at least, is neoclassic art. If there's him, Knuckles and an Emerald, you know there had to be a Sonic face one planned as well. These were likely to have been sold as a set of some kind. Why didn't they release it?
Well, they wouldn't do a good job against condensation, they're non-absorbant & have no rim...you'd just get a wet tile. The set (if it gets released) will appear on USA Home Goods & this entry will update.