Answer the question about text:

He seems like he 's mentally impaired somehow . As I ' m going through the spiel , asking him what size what bread what sandwich what cheese , my coworker ( we 'll call her Smash ) mouths to me , " HE 'S SO DRUNK ! " Ahh , that 's what it was .

Why does the person come off as mentally impaired ?
They are inebriated .