Gherkins were a type of vinegar-based pickled food.
In 2006, Jackie Tyler and Mickey Smith used gherkins and other vinegar-based pickled foods to destroy a Slitheen. (TV: World War Three)
The Tenth Doctor once got TARDIS' food machine to produce food pills with the flavour of "chocolate, pickled gherkins". (COMIC: The Glutonoid Menace)
Guy Burgess thought that the people of Moscow ate cold pickled herring and gherkins for breakfast. (PROSE: Endgame)
The Third Doctor used slivers of gherkins to make sandwiches for himself, Jo Grant and Iris Wildthyme. (PROSE: Verdigris)
Lucie Miller's Aunti Pat liked to eat gherkins. (PROSE: The Great Escapes)