I had a cat once that would have absolutely nothing to do with the sink. As soon as he saw me walking toward it with him in tow, I was shredded to pieces.

So, I decided to wet down an old towel that was sort of thinned by usage, I would lather up some shampoo in it and then I would sit on the floor with some kitty treats. Kitty would come to me and let me put the wet towel around him and rub him with it. I also had his favorite cat brush right there too to give him further cleaning with that. Then I would get another clean towel and rinse him with it. He enjoyed that kind of bath, just not getting into the sink. Go figure LOL

Good luck with the bathing!

Hugsssssss
J