Is when a guy shits
(the chili) between a womans breast
(the buns), and the guy sticks his cock
(the hot dog) in the shit and proceeds to titty fuck
her as she sucks the tip of his dick at the same time, eating the shit (the diet). Hence, the "Chili Dog Diet".
My buddy John keeps his bitches on a Chili Dog Diet then sends them home to kiss their husbands and children good night.