> goods and brands that claim sustainability as a value... Claiming sustainability and being sustainable are two different things. For instance "C&A" is making a lot of things from "Bio Cotton", but you if search for Bio Cotton on their website https://www.c-and-a.com/uk/en/corporate/company/sustainabili... you find this:

"BIO COTTON is all of that. It guarantees you that no genetically modified seeds are used, it supports farmers, saves the environment and feels good for you and your loved ones."

Maybe I am biased (I am not opposed to GMO), but I have doubts that this is the best way to be environment friendly.