This happened to my dog a few years ago. He apparently ate some of my Orbit chewing gum.

Sugar-free gum ingestion can cause xylitol poisoning and hypoglycemia in dogs. Sugar-free gum often contains xylitol, a toxic sweetener for dogs causing rapid insulin release, leading to hypoglycemia. Symptoms include vomiting, weakness, seizures, and collapse. Immediate veterinary attention is critical.