This is very French
so bear with me.
Until quite recently, in Paris, there were public outdoor toilets called Vespasiennes.
These men, called soupeurs, used to hang around in overcoats outside the toilets waiting for someone to arrive. When someone did arrive, they'd jump inside and put an old lump of bread, sometimes attached to a string, in the toilet. Then they would wait for the visitor to urinate on the lump of bread. Then they fetched it and sucked on it for hours. That's right.
Actually it's a sexual "practice". It's not an urban legend. It's true. Lots of Parisians remember lumps of bread in public toilets.