Based on an RP I did.

While on a beach trip, Sonic was upset that he was the only member of his group that couldn't swim, and nagged Tails into using science to make him a quickfix. Tails managed to put together a shampoo solution designed to give Sonic the ability to repel water from his body and let him easily float. However, as Sonic forced a rush job, the solution also made it so Sonic could also absorb water. He managed to figure out a way to use careful absorption and expulsion to develop a form of shapeshifting, though that and a few other events swirled up his brain and caused him to think he was a babe named Saphi. Now unrecognizable to her friends and lacking the brainpower to think of a better life plan, she now spends all of her time on the beach, using her powers to make her appeal to the specific kinks and desires of whoever takes the time to ogle her. Provided they buy her a snack or something.

Note: While not really a slime girl or anything of that like, her brand of shapeshifting leaves her in varying states of solidity and softness.