Vinegar
From Tardis Wiki, the free Doctor Who reference
Vinegar was a human-made preservative for flavouring foods in the 21st century. Vinegar featured predominantly in chips. Vinegar also contained acetic acid, which could kill Raxacoricofallapatorians (because of their calcium-based biology). (DW: World War Three, SJA: Revenge of the Slitheen)
