> In the Netherlands, where I live[...] Why is Coca Cola allowed
    > to sell their beverages (e.g. by the FDA) when there are "secret
    > ingredients"

It seems like you're implying that because Coca-Cola is an American product they can get away with this, but if it were manufactured in The Netherlands or the EU they couldn't.

That's not true. The exact same thing applies to food products manufactured or sold in the EU. Food labels aren't required to exhaustively list everything that goes into the product, or to publicly document the process by which the product is made.

Edit: I know Coca-Cola is manufactured outside the US, but I don't know if it's from scratch. I have a friend who used to work at the Coca-Cola plant in Iceland, and all they did was mix sugar, water and some nondescript "goo" they got shipped from abroad and carbonated it. So what went into the "goo" wasn't local knowledge.