Ah, the sink. I used to have to move a cat every time I wanted to brush my teeth. My husband and I have identical sinks, and at the time (before kids) the unused bathroom had two unused sinks, but she had to sleep in mine. I would literally be batting her away while rinsing my mouth. She had toothpaste spit on her more than once. It was perfect Doozy Cat sized, and she must not have minded toothpaste because she was always there. But why that particular sink?
The cat tower is a worthy offering, they just needed to show that they rule the world. Once they had played their mind games, they could accept to offering.