Based on a comment in /hardcore, I tried smashing a fortune cookie, and mafia increased my fullness by 1. The URLs involved are:
inv_use.php?pwd=stuff&which=1&whichitem=61
inv_eat.php?pwd=stuff&which=1&whichitem=61
inv_use.php?pwd=stuff&which=1&whichitem=61
inv_eat.php?pwd=stuff&which=1&whichitem=61