Yes, that would be pretty good. In the right kind of city. Buy a fleet of used food trucks. Pay someone to stick some labels on them. Find what local food trucks pay for produce and maintenance. Maybe ask some friend to drive them around town.
The only problem then is other food trucks would notice this fleet of trucks always driving around yet never stopping to sell anything.
They could sell something really simple -- just hotdogs. And it would be funny, other honest ones would see this plain hotdog business growing and expanding like crazy while they sell organic Korean bbq and don't seem to break even. So they go and expand into the plain hotdog market to capture some of the profits and then realize how unlucky they are when nothing sells. That's a plot of a short movie right there.
(Not fictional.)
Heck, you can launder money through restaurant without anyone in the restaurant knowing: Have people go in and buy a few hundred dollars of liquor at a time.
Some simple peer benchmarking of %cash vs %credit card transactions or looking at spend on produce vs revenue would likely show suspect operations quickly - I was talking to an auditor recently about similar benchmarking they do as standard but can't remember the context