(as) crazy as a soup sandwich

Completely unhinged, out of control, or in an incoherent mental state. This guy sounds as crazy as a soup sandwich. Do you have any idea what he's babbling about? Something about a "purple noodle sky balloon"? After seeing how she screamed at her students for the slightest infraction, everyone is starting to think she's just crazy as a soup sandwich. You kids are going to drive me crazy as a soup sandwich one of these days with all of your arguing.