So, if you worked at a drive-in, there are about 50 other customers to serve, there is only one other staff member, the manager had yelled at you that morning for being 1 minute late, the company is late on paying your min wage that you live paycheck to paycheck off of, non work issues happen like you find out your girlfriend cheated on you with a guy who used to give you a swirly in high school... all this and then you forgot to give the customer their drink. Or you don't exactly have a perfect smile, but try to be nice anyways. Or the customer almost yells at you for 10 minutes because there's not enough lettuce on their 1.00 burger. Because of this, they should be legally able to slap you. Sounds legit.