Yes, plastic bottles (and caps) are likely a major environmental disaster.
The alternative to regulation is innovation: force bottle makers to invest x% of their profit or revenue into actual research on plastic recycling or capture.
That's a very easy but hand-wavy thing to say.
How exactly would your suggestion work? Are the companies supposed to share their findings from this forced research with the world? What happens if they happen to discover something that doesn't help with the plastic problem but does improve their bottom line somehow? I can't see this functioning in any way whatsoever.