They can sell in non-plastic packaging.
They can invest in research of biodegradable packaging.
They can collect the packaging.
There's a lot a company can do.
There's a lot a company can do.
So we have to ask whether it is economically viable to, say, collect the packaging. I imagine that country-wide programs to do this would be very expensive.
Of the ones you mention, I imagine that research is the most likely to be viable (keep in mind it’s not just the research but also finding a material that is economically viable to produce) But how do you know they aren’t already doing that?
In Germany collection of bottles has been implemented all the time and it is definitely not "very expensive". In Slovakia it is planned to start again since next year or so.
In the 80's and 90's, where I live, Coca-Cola used to sell in returnable glass bottles, you would drop it at the mini market and buy a filled one, and buying one without returning another bottle cost a lot more, so people had incentive to store empty bottles and return it back. It worked just fine. They didn't go broke. I call BS that it's not economic viable.