Nescafe, the instant Coffee provider, is regular user of Gift with purchase items for its various promotional campaigns.  The following one is currently being promoted at ParknShop stores in Hong Kong.

Purchase a regular pack of instant coffee and receive an on-pack promotion a Winter themed mugs (Christmas style). The glaring red color of the mug and its package is an instant magnet for onlookers wondering about the brand of coffee they will purchase.

This clearly gives an advantage of Nescafe who, by offering this mug, get added on-shelf visibility thus increasing potential sales.

Compare this to the rather dull color of surrounding items and you understand how effective promotions and packaging can help differentiate a product from competition.