Hi and welcome
I have always fed Blue Buffalo and it has been great for us. Everyone has a diiferent choice here. Some use Canine Caviar, Fromm, and many others.
Treats that are produced in the USA are what you need to look for. And try to keep it low fat as Yorkies are prone to pancreatitis...high fat foods can bring this on. I give Mandie carrot sticks, green beans, and usually Zuke's treat bits