Yes, you have to do as foggydayz posted about the Sprite caps-perfect example of "lost" font superimposed on the green colour. Hold cap against monitor to see the "secret" iCoke PIN.
@Midnightly-yes, I have had issues with previous caps from Coke for PINs. Sometimes 3x entered and then an error message. Sometimes trying the PIN on another day worked. But the last time iCoke had the iTunes PINs, at least two cap codes would not be accepted for entry. I would re-read the date on caps and the days were still good...at least I did not bang my head over the matter.