Q. What do you do when you go to a county fair with one of your friends, and you both decide that the line at the girl porta-potties is too long?
A. You move over into the virtually non-existent boys' line.
Q. What do you do when you notice there's no sink facilities to wash up?
A. You deal with it accordingly by using extra toilet paper to minimize chance of contact between hands and biohazards.
Q. What do you do when you meet up with your friend again outside, and she informs you that there was actually a sink?
A. You ask her to describe it, because you obviously missed it.
Q. What do you do when you realize as she's describing it that she mistook the urinal for a sink and the urinal cake for a bar of soap?
A. Recoil, fight off the initial wave of nausea, avoid her flailing hands at all costs as you explain to her what it really was, fight off the second wave of nausea, and then spend random moments laughing your ass off at her for the rest of the night, long after she finds an actual sink and bar of soap.
Warning: She may not continue to be friends with you after this. I only offered general answers...I didn't say they were the best, most mature solutions.