I did this once with Denny's. Woke her up with breakfast I "just made".
Almost got away with it too until she found the receipt. Learned that day to never commit a major crime and then attempt to cover my tracks cause I'll definitely get caught.
Or don't create it. You don't need invoicing or books for an illegal business. Just have a rough idea of what your going to make and make sure you're close at the end of the month. Bookkeeping is just evidence for the prosecution. Its their job to figure out how long you've been in the game. The less they know the better your parole.
Whenever there's leftover pizza to reheat, on top I'll put chopped shallots that were soaked in olive oil, prosciutto, ultra-thin slices of fresh serrano chilies. If I have it, sometimes I'll substitute the prosciutto with thinly-sliced hard salami.
In a way, that's taking fast food and making it into my own thing.
Sometimes I'll bring a burger and fiddle with it the same way, like putting sharp cheddar on it and melting it at a low temperature on the toaster/oven. At the fast food place, I ask them to hold the condiments, so the bread doesn't get soggy before that.
If it's a more upscale burger - higher quality meat - I ask them to hold the tomato and onion, at home I'll substitute with yellow heirloom tomatoes with a spoonful of the shallots heaped on top.
Or I'll caramelize a full onion and put that in instead.
To top it all off, recently my wife pickled a large jar of sliced yellow beets.