The term Midwest Breakfast was adopted from a popular Midwestern service station chain, Casey's. To qualify as a Midwest Breakfast, a male and female fornicate the evening prior. In the morning, the girl performers fellatio on the man - consuming the leftover remnants that remain on the man's penis from the night before; presumably for breakfast.
"Debra and I did anal last night. She got hungry this morning and went ATM for some Midwest Breakfast!"
"Don't shower babe, I'm ready for some Midwest Breakfast!"