Personally I take a variety of tatics
-Old coke bottles with their dog food in it for them to chase around and empty out
-Hide their dog food in serval locations in the house or back yard for them to seek out
-Food Puzzles - Some boughten some handmade
-Peanut butter jars when there's not enough for a sandwich but still has some on the sides and bottom
-Bird seed/bread crums, Dogs love chasing the pidgeons out of the back yard.