pony keg

noun2

1. •
   (US) A container for beer holding 7.75 US gallons, equal to half the size of a standard beer keg.

   • Depending on the crowd, a keg or pony keg may be the way to go. […] For fewer than 20 guests, consider a pony keg, which serves 80 drinks. — 2006
2. •
   (informal) A drive-through liquor store; by extension, any convenience store.

   • A visitor may well be baffled by “pony keg” and “jack salmon,” but Cincinnatians know that the first is a store where beer may be purchased and the second is deep-fried pike. — 1967