Happy 30th Birthday Diet Coke!

Apparently, its Diet Coke’s 30th birthday and they are celebrating it by hiring brand ambassadors to throw 30-second birthday parties for brand loyalists, who also receive a year’s supply of Diet Coke.

How To: Win a Trip or Diet Coke for a Year by Checking-In on foursquare

HMSHost and Coke recently launched a check-in contest on foursquare that could net you a free trip, free Diet Coke for a year, or other prizes.