A phrase meaning to go out to the pub or bar in order to consume alcoholic beverages. Usually used to mask the real intent of the trip for the sake of children and/or the wife. Commonly used in Leicester, United Kingdom.
"Put the kids to bed luv, I'm just popping out with Jim for soup of the day"
Child: "Daddy, why do you come back on Saturday afternoons shouting and smelling funny, where do you go?"
Father: "Just out with my firends for soup of the day princess."