Pldennison and Doctor Jackson, I checked snopes.com and after digging around found an analysis of Nova and #9. Basically, “no va” does indeed mean it doesn’t go in Spanish, but “Nova” doesn’t. For #9, indeed the Coca-Cola name in China was first read as “Kekoukela”, meaning “Bite the wax tadpole” or “female horse stuffed with wax”, depending on the dialect.
I can’t find any info about the other slogans. Jens says that Mist does indeed mean manure in German. Although it is not slang, it is not something people would want in their hair.
So, as far as I can tell, these slogan blunders are not a total hoax. They have some truth in them. Perhaps they exaggerate the circumstances and interpretations slightly. I don’t see that posting them here does great harm, though. This is not nearly as bad as hoaxes such as the ones about AIDS that ask the reader to immediately forward it to everyone they know.