How can something that has contact with food be allowed to be secret?
It's similar with banknotes. The materials used is public knowledge (and parts of it patented), but manufacturing is a secret to avoid counterfeiting.
If you don't have a list of all the input raw materials, intermediates, by-products, impurities, surface materials that can leech into the final product, etc; you can't test for them.
As far as I know the only European company that is allowed to do that. And I swear that drink does still contain some alkaloid magic, even thought there obviously is no cocaine in it.