Welcome to Yorkie Talk. Mr. Scruffles is an adorable name. You will have to share photos.
I agree with Wylie's Mom. Maybe he doesn't like the taste of the Karo or the treat anymore.
What time of day did he throw up and almost throw up? What color was it? When my Teddy was a puppy, he sometimes threw up yellow bile with a little white foam. Usually in the morning. This is an indication that the stomach is empty and hunger is making them nauseous. I solved the problem by giving him a few kibble late at night before bedtime. Same thing can happen during the day if they go too long without food. Puppies tend to have really fast metabolisms.
Other possible causes, that Max suffered: getting overheated on a full stomach, getting too riled up on a full stomach.
There are many more potential reasons.