Raiders threatened staff with a syringe after leaving a store without paying for goods.
The two men picked up 15 jars of coffee from the Co-op store in Goring Road, Worthing, at 1.10pm on Saturday.
They put the goods into a holdall and began walking out. Staff approached them but were threatened with the syringe.
The pair are thought to have escaped in a vehicle waiting at the nearby Iceland store.
Police are appealing for witnesses.
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