Yes. Workplace and institution canteens can serve food to employees. This also applies in case the canteen is operated by an independent contractor.
Workplace canteens to which only employees are admitted are not deemed to be restaurants, and the requirement to wear a face mask or shield does not apply at the canteen.
The Danish Health Authority's recommendations should be observed in those situations
Canteens to which members of the public are admitted, such as canteens at educational institutions and workplace canteens also open to outsiders not affiliated with the workplace, are considered to be restaurants if the food and drinks are consumed at the location. In such cases, the canteen must stay closed to the public.