Dirty Sandman
When having unprotected anal sex with a woman/man, you use Nyquil as lube, pull it out and ejaculate in her mouth... the mix of warm bodily fluid and flu/cold relief liquid will promptly put her to sleep. You may then continue to have sex with her, but a true gentleman calls it a night too.
When Geoff gives Kate a Dirty Sandman, he uses cherry Nyquil so she wakes up with a better taste in her mouth.