The Australian actress was out to a date with husband Tom Ackerley in Mimi’s in the beach side suburb of Coogee when she ordered a round of drinks.
The 33-year-old offered fellow diners cocktails made with her own brand of gin, called Papa Salt, which she co-owns with her husband.
All 126 diners present at the eatery were treated to a free drink courtesy of the Barbie actress.
‘We just came for lunch and I unexpectedly saw Margot and she shouted the whole restaurant one of her drinks,’ one diner told the Daily Telegraph.
‘She was extremely approachable and made everyone feel like they were a part of her lunch.’
Another diner said: ‘Everyone, young and old, were wanting photos with her. Some people were crying they couldn’t believe their luck.’
Leaving the restaurant, Margot looked absolutely joyful, and was beaming from ear to ear.
She opted for a cropped black shirt with cut outs at the front that showed off hints of skin.
The star added a micro mini skirt with a checked pattern in tones of black and dark grey.
Margot completed her look with a pair of patent Mary Jane shoes and designer sunglasses.
For makeup up, she chose a warm, natural palette and wore her blonde hair down and straightened.
Margot and Tom are on a tour of her native Australia, having visited the Gold Coast, Perth and Sydney in the last few days.
The actress was born and raised in Australia and her siblings, including influencer Cameron Robbie, still live Down Under.