Shakeer, 42, Mohammad Matin, 28, and Sorab Alam, 24, were arrested Sunday near Malviya Nagar Metro Station in south Delhi.
"As many as hundred tablets of a sleep-inducing medicine and robbed items were recovered from their possession," said Sanjay Bhatia, additional deputy commissioner of police (crime and railways).
The trio revealed that they used to drive autorickshaws. While one of them drove the vehicle, the others posed as passengers. They then went to railway stations and bus stands and induced other passengers to share the vehicle.
"On the way, one of them would offer the victim a cold drink laced with the sedative and rob him as soon as he or she lost consciousness," Bhatia added.