It’s a non-toxic natural air freshener.
The “smell” goes away fairly soon once in it’s been poured out into a bowl and it absorbs odors.
[the mystery wasn’t that exciting after all, was it?] ...;]
I use baking soda for air freshening. I put a few drops of lavender oil in it in a shallow bowl. You have to change it fairly often, though. I put the used stuff in the vacuum cleaner canister.