That would be my concern too. However, I've tested some of my own pill bottles, and whatever plastic they are made of seems impervious to gasoline, oil, ethanol, carb cleaner, etc.Not worried about the interaction of fuel and plastic? Imagine that melted and heading for your fuel pump and multiple carbs.
Oh, it's nothing illicit, as far as you knowRadall- I don't even want to know what you are hiding in pill bottles in your tank