Liam Darby was a familiar face to cashiers at the Labrokes store in Gosport, Hants. When he threatened them and ordered them to hand over cash they thought he was joking.
Shop assistant Wayne Newman told him: "Liam, what are you doing? You come in here all the time, you're on CCTV."
When Newman realised Darby was serious he handed over £1,600. The thief, 20, dropped most of the notes as he rushed out of the door.
Darby's barrister Barry McElduff described his actions as "idiotic".
"One can scarcely think of a robbery of a shop that was more likely to come undone than Mr Darby's behaviour in his local Ladbrokes.
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"A place that he regularly goes into and a place that when they approached the counter the staff thought he was joking to begin with because they know him so well.
"Having been given the money by an employee, Mr Darby is so drunk he is dropping the money as he leaves the store."
Minutes before the raid Darby, who has a distinctive shaved eyebrow and tattoo on his neck, went into the nearby Co-op and threatened staff with a can. They ignored his demands for cash.
A customer told Darby to "just walk away" after he demanded their money.
Mr McElduff said "They were drunken, idiotic, spur-of-the-moment offences for which Mr Darby hangs his head in shame."
Father-of-one Darby was arrested four days after the raid.
He pleaded guilty to robbery and attempted robbery at Portsmouth Crown Court and was jailed for two-and-a-half years.
The court heard Darby had previous convictions for theft and assault and had been given a number of community orders which he had breached.
Recorder Stuart Jones QC said: "You have thrown away a lot of chances. These offences mark a serious escalation in your criminal behaviour."