Mark Megan punched the woman on her head causing her to fall to the floor of the Atlantis Bar in Kilbowie Road.
The 57-year-old later pleaded guilty to the November 2 attack, which was aggravated against his partner or ex.
Megan, previously of Kilbowie Road and now of Pappert, Alexandria, returned to Dumbarton Sheriff Court on January 20 for sentencing.
Sheriff John McElroy KC ordered him to do 120 hours of unpaid work in the community within a year.
There will be a review of his progress in April and a potential non-harassment order will be considered later.
