Small bottles of Magic Smoke, they are sold in pawn shops and bought to be used by Magic Users who need or want to have those powers for a short amount of time.
Depending in the type of magic or the quality of the smoke, they can be really expensive and highly demanded, there are monopolies of smoke types, like Shaitan who controlled the distribution of Heal-type smoke.
Ebisu used to be a smoke dealer selling her transformation-type magic for high prices, making her quite wealthy and demanded for her "Cool reptilian transformation magic" as the labels of her flask said.
2 years prior the events of the series, Dokuga, in hopes to help the Boss to escape from the creature haunting him, opened a door to Hole and gave him many smoke bottles, one of them, a reptilian transformation type, was the source of the character we know as Kaiman.
Nikaido, in great need of money to contact Asu, sold a flask of her unique type of magic and received a huge amount of money for it, yet she took it back, destroyed it and killed the pawn shop owner to ensure nobody ever knew her type of magic.
Investigating the sudden murder in a pawn shop, the Goons found a bottle of Ebisu's smoke and tried to discover what kind of magic she had (because of her mental breakdown, she was unable to produce any magic). Her magic proved to be incredibly powerful, transforming Noi into a gargantuan monster who killed a lot of Goons and almost slaughtered Shin, just with Chota's help she was able to be healed.
After the merge of Curse and Risu, Ton and Tetsujo where seriously wounded. In need of some heal-type smoke but unable to bough any because they were so damn poor, Dokuga disguised himself as a girl to sneak in Shaitan's mansion and poisoned to death everyone in the place, and stole all the heal smoke for the Cross-Eyes, this proved to be vital in the comeback of Kai.