This happened a while ago with the sub/cuck couple I had at the time.

Anna and I had already fucked a few dozen times and we've let his cuck bf watch uf from time to time. One of his kinks was cleanup after I was done.

During one of the weekends we were spending together, myself and Anna woke up and went to the kitchen to have coffee. As her bf would use the guest bedroom while I was there, he only realised we were up when we were already drinking our coffee.

In the process of making coffee, Anna had a great idea. She went on her knees, got my cock out and started sucking it. As usual she collected every bit of cum in her mouth, making sure to get every last drop. But instead of swallowing it like a good girl she spat it a 3rd cup and then proceeded to pour coffee over it and stir it. When her bf entered the kitchen she handed him the cup and gave him a kiss on the lips.

I was barely holding my laughter in and only gave in when he realised there's some stuff floating around in his coffee.

Needless to say he drank it all and even saw a buldge starting to form in his trousers.