Well, their employees had to do all the work to make that food without the franchise getting revenue for it, but the employees were presumably still paid
But the people were already there, it only happened over the course of a single day; it's not like they paid the people more because they were busier or making more orders.
They can only handle so many orders in a given hour. If too many people took advantage of this, then queues probably got longer, discouraging potential customers.
Customers, who would've paid nothing anyway, presumably
I don’t know about McDonald’s but I knew a manager at a Taco Bell and a lot of this fast food takes very very little work to make. Many Taco Bells can run on just a couple people when they’re not having to clean or maintain anything.