This seems to be in no way official but a prototype of the nostalgic juice flavor has popped up for sale on Ebay.
According to the description, it's just an empty sample can for a new line of Ecto Cooler drinks in support of the new 'Ghostbusters' movie. The seller got many questions (and apparently some abusive emails) as to how he or she came to be in possession of this rare item. They provided this statement in the product description:
For the threatening emailer (who needs to learn how to spell) and any others interested, this was sent to a friend who used to work for a marketing company. My friend hasn't worked there in a long time and received this via UPS or FedEx the other day. It was in a plain box with a box containing these inside. No paperwork. It's not stolen, nor is it marked "Sample" or "Not For Resale" that's why eBay has allowed this item for sale (and yes, I called them to verify at 14:04 EST 2/18/2016).