One hot and turbulent day I drank more water with my lunch than really needed to combat dehydration before seeing off from Cherbourg to fly the rest of the way home to Chauvigny. Now you can accuse a cub of many things, but not of being fast. After a couple of hours I really needed a convenient bush to provide cover for a quick wee. Fortunately one of France's many grass fields was close to track so I dropped in (Monday, so didn't expect anyone else to be there) and taxied clear of the runway. Shut down and jumped out, just about to enjoy watering the grass, when a whole lot of happy pilots rushed up to greet me and offer me a drink to compensate for missing the previous day`s airshow.
They were off course the tidying up party. Yes, they had a loo. I got there in time.
I think that's technically a landing to use facilities not available on board.