This is the shocking moment a McDonald's worker was filmed brutally beating a customer after she allegedly tried to fill up a water cup with free soda.

The brawl was posted to Facebook and Instagram by Nevada resident Marie Dayag, who said the fight started when the customer tried to put soda in a free water cup.

Dayag wrote: 'The lady asked for a water cup and supervisor shut down the soda machine because she wasn’t letting her get a free soda.'

A McDonald's worker was filmed brutally beating a customer somewhere in the US after the female patron threw a milkshake at her (left) and hit her with a tray (right)

Dayag's video shows the two women arguing before the fight breaks out.

While the audio is difficult to hear, the row appears to be over money. At one point the woman behind the counter can be heard saying 'since you can't afford one'.

The customer can also be heard saying 'that's why your a** is behind the f***ing counter' before throwing a French fry across the restaurant.

She can also be heard repeatedly shouting 'fight me' across the restaurant.

Dayag's Facebook page says she lives in Las Vegas, Nevada, and was born in San Mateo, California. It is not known where the fight took place.

A second piece of footage shows the fight breaking out after the customer hurls a milkshake at the employee.

As the staff member storms toward her, the customer picks up a metal tray and hits her in the head with it, but she barely notices.

Instead, the worker grabs the customer by the hair and begins raining punches down on her head and face.

The employee rains blows down on the woman's face and head before body-slamming her into a table as other staff members and a customer try to intervene

She then picks her up and throws her over a nearby table as other employees and even a customer runs over to try and break it up.

The pair are eventually separated as another McDonald's worker tries to move the customer away, but the customer then begins fighting her instead.

That restarts the brawl, with the customer beaten in the head and face a second time before the original employee throws her over another table.

At one point the staff member can be heard shouting 'my momma aint dead, you respect my momma,' though it is not clear what this is in reference to.

The customer also picks up a chair and makes as if she is about to hit the employee, but is quickly disarmed having apparently given up all hope of winning.

A few more angry words are exchanged but no more punches are thrown before the footage cuts out.

At one point during the brawl the worker can be heard yelling 'my momma aint dead, you respect my momma' - though it was not clear what this was in reference to