An allegedly intoxicated man stole a truck from a construction site and drove it through a cafe in Sydney's CBD in the early hours of Wednesday, police say.

Police were called to George Street just after 2am to reports that light rail construction workers had detained a man who stole a truck from their worksite.

The truck crashed into Regiment CBD cafe in the city, before construction workers dragged the driver from the vehicle. Credit:Steven Siewert

The construction workers told police an unknown man hopped into a three-tonne truck that was parked at the light rail construction works near Martin Place.

The man allegedly drove the truck through the work site on George Street, before it crashed into the front windows of the Regiment CBD cafe.