here's what happens to plastic bottle caps

 a plastic bottle cap is born when it is pooped out of a machine and then mechanically attached to plastic bottle. then it sits in a store for what feels like forever because a plastic bottle cap has no sense of time. but it's also no amount of time and also forever. Then the drink gets purchased by me Andy and I consume the liquid and turn it into me but get rid of most of it where it ends up in the water cycle and probably the carbon cycle a little bit too. And maybe the dirt cycle. Anyway I keep the bottle cap and put it in my junk drawer by my coffee machine to mature and gather energy.

Once it has sat long enough and the weather gets nice then I take it out of the drawer and use a sharpie to inscribe an ancient and future rune on it and put it in a bag with other bottle caps that have undergone a similar process.

Now that bag sits on my shelf until I decide to take it to the rock climbing gym where it sits in the setter's closet and gathers energy there. 

I know what you're thinking. How's he going to save the world? How will this save the world?

Guess what, idiot. The world doesn't need saving. Because the world is the world and can't be destroyed in any meaningful way. That's where the bottle caps come in. One bottle cap is special and will be cast forward into time where it will absorb energy from the sinister sun that will appear next to our regular sun out of nowhere ten thousand years in the future. The sinister sun can destroy the Earth in a meaningful way.

But because I've sent the bottle cap forward in time to absorb energy from the sinister sun, it can return back to the present and incubate inside the Earth like a vaccine. And the Earth will develop antibody bottle caps that will sprout out of trees when the sinister sun radiation hits. Those bottle caps will destroy the sinister sun and fulfill the prophecy.\

I don't really know though your guess is as good as mine.