I think it is very clever what they did to make it possible. Follow the link and find out what was done to it.
It is not exactly contained in the vehicle but I still think it qualifies as a 'food truck' and in it - sort of - is in one vehicle.
Here is a Youtube video of the Smart Fortwo (ForFood?) food truck.
The Chicago Tribune has the story for this one - a breakfast burrito 'truck' - at the link above. I like the color and that it uses a Smart Fortwo. I wonder how well a Smart Forfour would work?