I -think- it's basically a "gravy" that some dog food companies have made, as a top dressing for dry kibble. There used to be commercials about it on tv, but I haven't seen those in a very long time. Makes me wonder if it was a passing "omg we must try this" thing, or if something bad came out of it.
That being said, you can always make your own "gravy". Or well... you can make stock soup to soak kibbles in. You don't even have to use the actual meat either, you can just use bones.
Say you want to make chicken for dinner, and instead of buying boneless, by chicken with the bone, debone it yourself, and use the meat for your meal. Then, you can put the bones in a pot of water and let it boil, and then turn down the heat to simmer and reduce the water a bit. And voila, you have your own homemade no additive stock that you can use to soak some kibbles in.
This can be done with any type of bone, chicken, pork, turkey, even fish bones.
Of course, you can also use meat in there as well, but the bone works just as well.