Just noticed this today. The website says it's been valid since March 27th, but I've not seen it in-store before and I've been checking!! A 12 pack for the price they usually charge for a 6 pack. Presumably they haven't got much choice with these since the packaging quite blatantly says 6 cans free lol
I couldn't see this already posted, but it probably has been- so feel free to spam if necessary! Valid till this Sunday (well, until the next Pepsi offer).