Empty Can! (2009)
How could Kakeru Diachi, who collects rare juice cans, have ever suspected that he'd meet a fascinating new girl when he attempted to DRINK her? Naming her Melon, because she's got great melon - soda, Kakeru quickly learns that she's an Akikan-a beautiful girl who's also a special can created to fight other Akikans in a strange experiment to determine what kind of container is better: steel or aluminum.