Cain's sexual orientation is a secret, according to Hamlet. Although its rumored that this sexual orientation is bisexual or pansexual. Given the only thing to support this is a term Cain had said to Abel during sex.
Cain's favorite dessert is whiskey and a pack of smokes.
According to HamletMachine, "Cain would like to think he knows a lot about life on Earth from movies.. but he really just has a vague idea of what goes on there... he doesn’t know too many animals besides a small variety of Earth-imports."