Sonic bath balls!
Make your bath scented, fizzy, and fun with Sonic bath balls. These are also sometimes called 'bath bombs' 

There's one aqua blue colored ball in each bag style package. But, the balls have a surprise inside! Once they fizz / melt into the bath to make the water nice, they reveal a little plastic toy.

The toys are the 'little cuite' style for Sonic, Tails, Amy, Knuckles & Shadow. They're blindboxed inside the balls, so you never know who you'll get until you take a bath. These may look like the regular type Tomy bagged items, but if you see the packaging backs/tops it's in Japanese so this is the market that had them first. The scent of it is supposed to be mint. Do you want to see it in action? There's a Sonic Bath Ball Using Youtube Video where they reveal the figures. (But, its in Japanese)