They look like regular Japanese tsukimidango.
What Does It Do?Edit
Although aliens face no side-effects, the Earthlings will turn into werewolves, in case they eat it.
Ataru eats this concoction against his better judgement and winds up slowly changing into a dog. Onsen-Mark eats it and begins to change as well. Ataru decides he'll teach Lum a lesson and runs away, refusing to take the antidote. Luckily, Lum is able to track him down and give him the cure.