Pull tabs
Before plastic was the great environmental villain, detachable aluminum soda can pull tabs like this lying on the ground were the great enemy of the Earth. Or not.
I remember at the bottom of my soda cans - Orange Fanta, I think it was - there was a joke or riddle printed. On hot summer days, I drank the drink then squinted into the can trying to read the message off the bottom. Hot summer days still remind me of the taste of Orange Fanta - not Cream Soda or Root Beer, which were other popular drinks - but Orange Fanta.