Green’s Dictionary of Slang

1. (US) a bottle of bourbon.

1862

W. Babcock Sel. from Letters and Diaries (1922) 94: A ‘muggins’ is a bottle of whisky, and a ‘big muggins’ is a gallon jug full.

2. (US prison/tramp) food.

1933		Ersine Und. and Prison Sl.
1949		Monteleone Criminal Sl. (rev. edn).