Sarah Douglas asked for the coffee at a drive-thru in Alberta, Canada last Sunday morning, but when she took a sip she immediately knew something was wrong.
Douglas pulled over and spat out the liquid, saying she opened the "lid of the coffee and out pours this pungent smell of chemical."
Speaking to Lethbridge News Now, Douglas said she went back to the fast-food restaurant where one of the employees informed her two cleaning lines were hooked up to the coffee machine by accident, McDonald's later confirmed that the milk supply line was connected to the cleaning solution.
Douglas also noted that another worker said the incident had happened before and she was "a little mad that it was occurring again."
McDonald's has responded in a statement saying they have been in close contact with Douglas and have taken immediate action to review the proper cleaning procedures.
This article originally appeared on Marie Claire.