[1] - Contact Fiveguys: https://www.fiveguys.com/contact-us, say you & your gf got diarrhea eating at there restaurant.

[2] - They might ask how do you know that, say you and your friend only shared the same meal at there restaurant which explains how it's their fault.

[3] - The person might either send you a gift card or give you there personal number to call whenever you decide on visiting again, they will instruct you to call them when you are on your way there and they will call the restaurant saying you're coming and to give you a free meal.

[4] - I have the phone number for Brooklyn, New York if anyone is interested, you don't have to really see them one you have the number of the division manager of the place you're trying to see.

[5] - Just call and say you told me to call next time I visit and you said you would pay for my meal, they will ask for your name and then call the restaurant.

[6] - It seems like it's very common because the person who I talk to when I call always says "I have a lot of similar cases, what is your name so I can call the restaurant", I have done this about 3-4 times, I don't know how this lady doesn't recognize my voice.