Very well then.
Coke is, besides the popular name for cocaine (which used to be an actual ingredient for Coca-Cola until 1904), the informal term for any soft drink that tries to copy the original Coca-Cola in some way or the other. Of course, since the exact Coca-Cola recipe is kept secret, each company has developed its own specific distinct flavour that are now world brands of their own. Pepsi and Dr. Pepper being the best examples.
Dr. Pepper however, is slightly older than Coca-Cola, but since Coca-Cola was the most successful, it became a sort of unofficial standard.