I'm so glad soneone else has mentioned this. I thought it was only me that thought it strange. It's not cooking oil, the liquid is too clear (yes, I've peered at the bottles). It's can't be pee either (too orange!). And there are too many bottles for it to be an (drugs) advertisement. So... If anyone has any insights, do let us know. Several bottles appear, then are mysteriously collected. And it has been going on for a few weeks now.