>>2007691>In these glory days of rail safety, nobody wants a vat of hot oil sloshing around in a confined spaceMcDonald's was briefly contracted to handle catering for Deutsche Bundesbahn in the early 90s and they did manage to rebuild a pair of surplus dining cars into restaurants that offered the full McDonald's menu, using custom-built deep fryers similar to the ones used on ships.
From a technical standpoint, the project was a complete success. It only failed due to poor sales, poor logistics (restocking had to be done with McDonald's restaurants along the route instead of from fixed mid-journey stops), and the fact that the 90kW power consumption was very taxing on the cars.
https://www.thedrive.com/news/38221/the-mctrain-the-rise-and-fall-of-mcdonalds-ambitious-plan-to-conquer-the-railroads 