After teaming up with Pepsi for a pair of iTunes giveaways, Apple is now partnering with Coca-Cola for its Slurpee Summer Prize Fest promotion, which promises to give away up to eight million songs this summer. Specially marked 32-ounce Slurpee cups at participating 7-11 locations contain codes redeemable for free songs through the iTunes Music Store. Each cup contains one free song that must be downloaded by Aug. 31. The promotion ends on July 31.