There are, of course, many different ads for Coca Cola with somewhat different “hooks.” In general, though, the hook that Coke tries to use to attract buyers is a message that people who drink Coke are happy and in some way “cool.”
For example, this ad connects Coke to the joy of Christmas. It sends the message that people who drink Coke are the sort of people who could jump up, go outside, operate this giant Santa marionette and go around making other people happy. This has nothing to do with what Coke tastes like or its price or anything that is intrinsic to the beverage. Instead, it is all about trying to create an image of what people who drink Coke are like.
As another example, this ad portrays Coke as the drink of people who are active and athletic. Even though the protagonist of the ad is a polar bear, it is clearly meant to connect Coke with football. It is meant to claim that people who drink Coke are the kind of people who could make the sorts of athletic moves the bear made.
Thus, Coke ads try to hook buyers by creating an image of Coke as the drink of people who are active and athletic and fun.