How do you make the association if you can’t get the dog to show interest in the item to begin with? As soon as my 2yr old GSD knows the treat is in my hand, he is ONLY interested in the treat, not any number of toys offered to him.
I would recommend to teach the dog "touch" first. And then use that to introduce the toy. And the treats can be in a pouch not your hand . Only after they do what you are trying to get them to do then do you put your hand in the pouch to get the treat. Good luck!