Baillie Patrick from Birmingham has been jailed after attacking the van driver in the city last autumn.
The attack took place when the van driver spotted Patrick standing in the middle of a road in Shard End at 8.40am and stopped to see if he was alright.
At that point Patrick claimed the driver owed him money and launched into an unprovoked attack during which he punched the 41-year-old and assaulted him with a sledgehammer.
He also smashed up the Mercedes van, causing hundreds of pounds worth of damage.
Patrick, who according to police was drunk at the time of the incident on October 18, was arrested at the scene.
While in custody, he told officers he had no memory what happened, but later admitted his guilt.
The 24-year-old pleaded guilty to robbery, possession of an offensive weapon and criminal damage at Birmingham Crown Court.