A Somerfield store must have all of its alcohol products marked by police so they can be traced back to the store if they are found in the possession of minors.
The condition was imposed this week by a licensing panel at Brighton and Hove City Council. It is the first time the measure has been used in England.
The store on London Road, Brighton, was also given a one-month ban from trading alcohol coinciding with school holidays next year.
The branch has a history of failing test purchasing. Its licence was suspended for a month in February after failing Trading Standards and police stings. In June, it failed another two test purchases.
Following staff training by Trading Standards, another test purchase took place on 12 July, when the sale was refused. But in a sting on 1 November, three staff failed to stop a teenager buying a bottle of whisky, including the licence holder, who even walked the boy to the liquor counter.
The licensing panel approved a police request for a total suspension of the store's liquor licence for one month next May, when GCSE students are revising, and the introduction of ultra violet marks on bottles.
Somerfield said staff were under pressure because they were often verbally and physically abused for refusing to serve alcohol.
Inspector Bill Whitehead, Sussex Police's head of licensing for Brighton and Hove, said: "They have signed up to selling alcohol. If they want to do something simpler they could have just stuck with selling crisps."