I did something like this on a solo bike tour. Due to some rather messy geohashing the day before, I arrived at a restaurant (the only place open) in a small town completely filthy. I mean, covered in dirt, mud, and BO. After ordering, I snuck into the bathroom and used paper towel, soap and water to get vaguely cleaner, and put thermals over my knicks and jersey. I can't say I was really presentable afterwards, but perhaps I was no longer putting other patrons off their meals...