Edward Hankey committed the offence in Cheshire in September 2021, the Crown Prosecution Service (CPS) said.
There was video footage of the assault and the victim reported the incident to police on September 16, 2021.
Hankey was arrested the same day.
The 54-year-old denied the assault initially but pleaded guilty at Warrington Magistrates’ Court on April 14, 2022.
Hankey, 54, of Wendover Grove, Berry Hill, Stoke-on-Trent, was given an immediate two-year jail term at Chester Crown Court on Thursday (May 12).
He was also placed on the sexual offenders register for the next ten years.
The CPS applied for a restraining order to prevent Hankey making contact with his victim.
This was granted by the court indefinitely.
District Crown Prosecutor Brian Forshaw, a specialist lawyer with CPS Mersey Cheshire’s Rape and Serious Sexual Offences (RASSO) unit, said: “The Crown Prosecution Service and Cheshire Police had damning evidence of this assault and Mr Hankey thankfully pleaded guilty at an early stage. He has now been sentenced.
“The CPS would like to thank the victim for her help and courage in bringing this prosecution and we have worked to support her.
“The evidence she secured of the assault was crucial to this case and no doubt led to Mr Hankey’s guilty plea.
“Mr Hankey is now a convicted sex offender and this case may have prevented further offending.”