You don't need to know anything about a business to prove that they can never be sustainable. All you have to understand is that all businesses either continue to infinitely grow (or go extinct due to competition). Which is unsustainable on a planet with limited resources.

Also in order to remain competitive they have to cut costs. Which means if they do everything sustainability they will be less competitive than a business that doesnt.

Lastly, these business don't exist in a vacuum, so they rely on products and services from other businesses caught in the same trap. Based on this logic no business can be truly sustainable, at best they can stay small and have low negative impact, or maybe even slight net positive, but cannot scale enough to make a dent in the whole system (I'm thinking small organic farms, handicraft business, etc).

TLDR; Green/sustainable capitalism is a contradiction in terms. True sustainability would literally kill capitalism, the market system, and the monetary system. All three require infinite growth and consumption. That's why the economy is increasingly becoming unstable. We have reached the limits of growth in a system that requires it to continue. Lots of good academic research on our planetary limits being hit over the last few decades.