I frequently observe other trainer's classes and notice their methods are simply an exercise in
giving dogs treats as rewards no matter if they have completed the task or not.
So, it is best to
give your dog this treat in limited quantity and see how he / she reacts to it while being on empty stomach as well as after meal.
Normally, when we want to train a new behavior, we do this
by giving the dog a treat (or other reward) at the specific moment he does what we want.
Explain that you want your dog to view the vet office as a fun place to visit, and perhaps the receptionist could
even give him dog treats each time you arrive.
If you're in the habit
of giving your dog treats (or if you're training her, for example), the best course of action is usually to train her at meal time and use her regular dog food as treats / rewards.
Once he's consistently moving away from the first treat, try it again — But
only give your dog the treat after he moves away from the first treat and looks up at you.