Jake Tomkinson, 31, stole tea and coffee articles at the value of £ 80 of CO-OP in McLeod Road on January 29.
He was arrested and accused of theft of a store and possession of a knife in public.
Tomkinson, or without a fixed abode, denied both charges.
However, on March 24 he was convicted of the positions by the Bromley Magistrates Court.
On Tuesday, April 8, he was sentenced to six months of custody.
