Former PC Paul Hinchcliffe, 46, was drinking at The Church House on Saturday, October 3, 2020.
He made sexually suggestive comments towards a woman at the pub, while also taking a photograph of her and showing it to other people.
Hinchcliffe, of Wath, then flicked beer foam from the top of his pint at her chest area, pulled her top down and took another photograph.
The woman was upset by the incident and asked a friend to come and pick her up so she could leave.
An investigation was launched after a report was made to the force’s Professional Standards Department.
In an interview, the officer answered ‘no comment’ to all questions put to him.
CCTV obtained from pub as well as the photographs taken by Hinchcliffe on his mobile phone were obtained and used as part of the case.
Hinchcliffe was charged with one count of sexual assault, which he denied, but was found guilty by a jury at Leeds Crown Court earlier this year.
On Friday, he was jailed for eight months at the same court - and has been placed on the sex offenders’ register for a decade.
He resigned from the force and, following an internal police investigation, it was found that had he not resigned, he would have been sacked.
He has since been placed on the policing barred list which means he will never work in the industry again.
Chief Constable Laura Poultney said: “This case demonstrates that wrongdoing and poor standards will not be tolerated in South Yorkshire Police.
“Whether our officers and staff are on duty or not, the public rightly expect us to portray the true values of policing at all times and this former officer fell woefully below these expectations.
“I am mindful this hearing follows the release of the Casey report last week and wish to assure our communities that here in South Yorkshire Police we are doing absolutely everything we can to root out those who are not fit to represent your force.
“This particular case was investigated following an internal report to our Counter Corruption Unit, which demonstrates the willingness of the vast majority of our workforce to stand up for what is right.
“Force standards and culture continue to be my top priority and when wrongdoing and poor standards are identified, the perpetrators will be dealt with swiftly and robustly.”
She added in the report that in a time where incidents like this involving a police officer are of concern to the public, Hinchcliffe undermined the public trust.
“This is a conviction for an offence which would particularly concern the public, this is a conviction for a sexual offence,” she added.
“The public rightly expect police officers to protect women, girls and others from inappropriate sexual behaviour and being convicted of such offences particularly undermines the public trust.
“Public confidence in policing continues to be shaken by the conduct of police officers who perpetrate sexual violence against women and girls both on and off duty.
“Police perpetrated sexual misconduct is an area of particular public concern.”