According to an article from DogAge.com you should keep your dog far, far away from any food that is “sugar-free”. Most likely that “human-grade” treat contains Xylitol, a sugar-free sweetener.
You can find this very bad substance in some candies, gum, and even soft-drinks. I doubt many people give their dogs gum or diet soda but if you leave it around they might decide to try it. We dogs are curious beings.
I’m not always picky about what I put in my mouth. I may have swallowed a thing or two I’ve found in the street. Don’t judge me.
Anyway, Xylitol can cause low blood sugar, seizures and impair muscle coordination. If your dog does eat something with Xylitol please see a vet as soon as possible. Just saying.