Green’s Dictionary of Slang

(Aus.) (in SA) a beer bottle that can be returned for a refund on the deposit.

1984		E. Hale Catch the Sun 6: She grabbed the box of echoes and had the top off one as smooth as removing a cap from a milk bottle [AND].
1993		Sydney Morn. Herald 17 July Good Weekend 35/3: In Adelaide, stubbies are called ‘echoes’ because they are returnable .
2000		Google Groups:aus.politics 17 Jan. 🌐 Try that Red Back, but a word of warning, it is undrinkable UNLESS you first poke a slice of lemon down the neck of the echo, then it is a nice drop.