They pushed aside the 23-year-old male shop assistant who fell to the floor and threatened a woman shopper, aged in her 40s, who had just come into the shop.
The suspects grabbed a quantity of cash and left in the direction of the car park between the High Street and Brookside.
The robbery lasted no more than a minute. No one was hurt.
The suspects are described as two males, aged 18-early 20s. They were both wearing hooded tracksuits with the tops up.
Enquiries are continuing.
If you have any information contact Sutton CID on 101. Alternatively, contact Crimestoppers anonymously on 0800 555 111.