I had experience of similar machines when studying in Germany. They sold hot snacks like sausage rolls and other more Teutonic snackage, and were popular with the after-closing-time crowd.
The food in them was revolting in that artificial, heated-by-lamps way, and usually gave you the trots in the morning (if the Flensburger Pilsener didn’t). I remember a friend buying and eating them while drunk as like being in a car accident,
“You can see what is going to happen in slow motion, but no matter what you do, you can’t stop it.”
A similar tale revolves around my time at High Wycombe. There was a van which sold burgers and stuff after the oft-attended Attic nightclub closed. One speciality was the ‘Student Burger’, which contained 2 cheap burgers, salad and a fried egg. An excellent way to lose 2 stone over a weekend.