"how many quarts of porter have you in you?"
GNU Free Documentation LicenseGuinness - Credit: Liftarn

Porter is a dark-coloured beer, also called stout, brewed with dark malts. 

 1 quart = 2 pints.

The expression "Mind your p's and q's.", meaning watch your behaviour, may have derived from bartenders recommending patrons "mind their pints and quarts".