An abbreviation for your "standard order". This is your favourite drink, chocolate bar and packet of crisps that you could pick up at any petrol or service station any time of day. The drink can either be a soft-drink, can or bottle, or something else that is common. The crisps must be available in a bag, potato or corn, but nothing stupid like a whole tube of Pringles, for example. The chocolate bar is self-explanatory.
To know someone's stanny is a test of true friendship.
Joe is taking a trip to his local petrol station to pick up some sundries. Before leaving, he asks Polly if she would like anything. "Oh, just my stanny, thanks Joe," she responds.
(N.B. Joe has truly cooked his goose if he doesn't know what Polly's stanny is. They HAVE been together 7 years, after all.)