The reason there's no period is that they can name their drink anything they want. The lack of a period makes the label look slightly less cluttered. Rules of punctuation have nothing to with it.

The reason given by Consumer Relations may simply mean that neither the writer nor anybody at adjacent desks had the slightest idea why there's no period and couldn't find anyone else to ask.

Another interesting question is whether "Dr Pepper" once had a period that was later removed.