Before
I recently had a happy meal delivered with just a toy, napkins, and 6 packets of BBQ sauce in the box. It was supposed to be a hamburger happymeal and fries, and I had never had napkins put in a happy meal box before.. So I get where this guy is coming from, but I would not do it even if they asked TBH, because they can say you did something to the food, even if they consent to you opening it. I just don't trust it.
After
I recently brought a happy meal in a box with a toy, I gritted my teeth with 6 packets of soup. It was supposed to be hamburger with French vegetables, and I never put napkins in a delicious box. I can say you did something with the food, even though they agreed to open it I do not agree.