Police arrived at the scene in Santa Cruz de Tenerife after receiving a telephone tip-off, local daily Diario de Avisos reported on Friday.
An inspection of the vehicle revealed a man inside wrapped in a blanket. When he failed to respond, police called in an ambulance and the fire brigade.
The rescued 24-year-old man was in good health but still drunk, according to the authorities.
He said he had a vague memory of being bundled into the car boot by his brother, a cousin and another person.
In other news, a 27-year-old woman was on Friday arrested in the southern Spanish town of Fuengirola, near Malaga, after she left her three-year-old daughter alone at home so that she could continue her New Year's Eve celebrations.
Police were alerted when a neighbour spotted the child crying.