A Canadian McDonald’s store has apologised after a pregnant woman was served a cleaning agent in a cup instead of milk in the latte she ordered.

Sarah Douglas, who is eight months pregnant with her third child, ordered the drink at a drive-thru in the town of Lethbridge, in the province of Alberta.

Ms Douglas told Lethbridge News Now she was driving onto the highway to take her son to his baseball game when she took a sip.

“I immediately had to put my hazard lights on and pull over and spit it out and rinse my mouth out with … water,” Ms Douglas said.

I opened up the lid of the coffee and out pours this pungent smell of chemical. It wasn’t a latte at all.”

Ms Douglas said the liquid was a watery-brownish colour.

She immediately drove back to the store and told one of the employers she wanted to speak to the superviser.

“I showed him the coffee and he had asked if I wanted a new one, and I said, ‘absolutely not, this is unacceptable’,” Ms Douglas said.

She said the coffee machine was still undergoing a cleaning process, even on her return to the store.

The store in Canada where the tainted latte was served. Photo: Lethbridge News Now

Store owner Dan Brown later issued a statement saying his team had been in close contact with Ms Douglas and had apologised to her.

“We have taken immediate action to review the proper cleaning procedures with the team and have put additional signage up as an added reminder.”

Ms Douglas called the provincial health service and was transferred to poison control shortly after the incident.

She took a photo of the label on the cleaning solution so she would know what to tell poison control when she called them.

“Causes serious eye irritation. May cause an allergic skin reaction. Keep out of reach of children. Wear protective gloves/eye protection,” the label of the cleaning fluid warns.

Ms Douglas said she felt okay, but she would be seeing her GP as soon as possible.

-ABC