Chocolate contains a high amount of theobromine which is really toxic for dogs and can cause vomiting, diarrhea seizures, and even death in severe cases.
Even small amounts of grapes and raisins can cause kidney failure in dogs. In other cases, it can cause vomiting and loss of appetite.
Onions and garlic contain a compound that can damage a dog's red blood cells, which can result in anemia. This can also cause them vomiting, and low breathing in them.
Caffeine is a highly toxic compound for dogs, found in tea, coffee, and sodas it can cause vomiting, diarrhea, and increased heart rate.
Xylitol is a sugar substitute that is used in candies, sugar free gums, and baked items It can result in an instant spike of insulin in dogs and can cause low blood sugar that may result in liver failure.
Avocado contains persin that is toxic for dogs and causes them vomiting and diarrhea and even the pit, skin of avocado can choke them.
Even a small amount of alcohol can be highly toxic for dogs and can result in death or coma, in other cases it can also cause vomiting, diarrhea, and difficulty in breathing.