The first step in this economy is to get the customer into the store. Once the customer enters, you have a chance to make sales, one or many sales. When the customer arrives for the free product in the grocery or department stores chances are other sales will be made before this customer leaves.
It is human nature and you usually pass an item that you have always wanted or needed. Rarely does a customer have such self control as to come in for the free item and leave. The store should have personnel roaming the floor to encourage other purchases and to tell the customer what is on sale.
Gift cards are an excellent idea, because it has been proven that the recipient of gift cars always spends more than the price on the card. A year’s free groceries obviously is limited in some way, not just fill up your cart and leave without paying anything.
Here again if you give $100 of free groceries, much more than that will be spent, especially in a grocery store, where there is always something that you need or want.