I had to do it once. I was pretty drunk in college and ordered food. It turned out my friend had NO money and i had to pay for both of us but I only had enough cash onme for a 75 cent tip. i borrowed a dollar from someone smoking and gave it to the delivery dude so he wouldn't spit in my meal the next time he brought stuff over.
I ran upstairs and came back with a beer for the guy I bummed a dollar off of