Connor Haughey, aged 22 from Glengoland Crescent, Dunmurry, admitted robbing the north Belfast newsagents on the Antrim Road on 26 October, 2010.
Prosecution lawyer David McClean said Haughey had taken a can of Fanta from the fridge, which he left on the shop counter before producing a six-inch knife and demanding cigarettes and money.
Mr McClean also told Belfast Crown Court that Haughey, who was unmasked, was later easily identified following his arrest after his fingerprints were taken from the drinks can.
Defence lawyer Martin Morgan said while he had produced a knife during what clearly was an unsophisticated and amateurish robbery, no real violence was offered to the shop assistant.
Mr Morgan said that when Haughey had initially demanded cigarettes, he was asked which brand and then only given two packs.
The lawyer said while an intelligent Haughey had blighted his life by his abuse of solvents and alcohol he was "a young man not without hope".
Mr Morgan said he had clearly shown remorse and regret for his actions and was a person who would benefit from extended supervision on his release from prison which would also help provide future security and protection for the public.
His Honour Judge Kinney told Haughey he had caused his vulnerable victim fear and distress and that such raids on small local businesses had an impact on the general public.
However, he accepted that Haughey would benefit from an extended period of supervision after his prison release and ordered he serve 18 months custody to be followed by two years licensed parole.