The teenagers were hit by the vehicle during a road session which was being held near their cycling club, a police spokesperson said. They were all hospitalized, although none of the injuries were believed to be life threatening.
The cyclists aged 12-18 were experienced riders and were in training for Polish, European and world junior championships.
The driver, who veered across the carriageway, may have fallen asleep at the wheel, but he was not drunk, the country's PAP news agency said.
Police said the man attempted to commit suicide soon after the incident. "He wanted to hang himself on his seatbelt," the spokesperson added.