Many moons ago, I was eighteen and on my first trip to Europe. I met two young American women in Heidelberg and we became friends. They were living in Cologne and suggested I stop in to see them when I was on my way back to Frankfurt. I did so, and stayed overnight. (No shower, just a plastic tub they put in the dining room.) We went to dinner at a restaurant of their choice. They said that there had been some sanitation problems recently, but it had been taken care of. (You're getting the picture, right?)
I took the train to the Frankfurt airport, ready to fly home. An hour before the flight I became ill. Thinking it was too late to turn around, I boarded, not realizing that once you're in the air, an upset stomach just won't settle down. I heaved for the entire fifteen hours of the flight. There was no drinkable water on board, only some grapefruit juice, IIRC. I felt so bad for the woman seated next to me, who was quite stoic about it. Once home, I was sick for several days. But very glad to be home.