A police operation was mounted to catch out shops in Sheffield serving alcohol to children.
Members of the Sheffield South East local policing team visited 15 shops and found one breaking the law.
The team covers areas including Beighton, Birley, Charnock, Frecheville, Gleadless, Hackenthorpe and Woodhouse.
A team spokesman said: "Fifteen premises were visited and one sold alcohol to our underage volunteers.
"The premises will be revisited and further checks made in the future."