There is a supplement called NUPRO (not to confused with nutro the food) that is excellent. It is a powder and you mix a tiny scoop (about half a teaspoon) with a little warm water and it makes a gravy that you can mix with kibble. In addition to making the kibble yummy, it makes their coat shiny and is full of vitamins.
Here's a link.
NUPROSUPPLEMENT.COM