PC Daniel Moss, 39, who was based in Hastings, was placed under formal investigation by Sussex Police on 2 December and suspended from duty.
The force said he was advertising sexual services for payment on an adult website after reporting off sick with a stress-related illness in September.
He was sacked on Friday following a public gross misconduct hearing.
The hearing found he had behaved in a manner that had discredited the police service or undermined public confidence.
He did not attend the hearing.
Det Insp Nick Wainwright from Sussex Police's professional standards department said despite being on sick leave Mr Moss was "still able to offer himself as being available to perform sexual services for payment".
Mr Wainwright said it was "clearly completely out of keeping with his role that others uphold with pride, integrity and with the trust of the public whom they serve".
A police officer who advertised himself as a male prostitute while off sick from work has been sacked.