The story
An elaboration of fair go (used in protest to implore or demand that someone act with more fairness or reason). Sauce bottle appears to refer to a bottle of cheap beer or another alcoholic beverage; see sauce (“(slang) alcohol, booze”).
First known use, by meaning
- from 1970s A fair chance, a reasonable opportunity; a fair go.
- from 1970s Used to protest against unreasonableness, such as somebody taking more than their fair share.
Etymology from Wiktionary, CC BY-SA 4.0.