Many foods are not good for dogs to eat. Some may cause unpleasant symptoms, such as diarrhea, but others can cause fatal reactions, so it is a good idea to know which foods you should not give your dog, no matter how longingly he looks at you.
Any beverage or food that contains alcohol produces effects in dogs similar to those it produces in people; however, it takes less alcohol to produce those effects in dogs, especially in small dogs. Vomiting, diarrhea, coordination problems, breathing difficulties, coma and death may occur when a dog ingests alcohol. 
Avocados contain persin in the leaves, seeds, bark and fruit, a substance that may cause toxicity in dogs. 
Caffeine that is present in coffee, chocolate and other foods can be fatal to dogs if eaten in large quantities. Methylxanthines in the cacao seeds used to make coffee, chocolate and certain sodas can cause vomiting and diarrhea, panting, seizures, heart arrhythmias, and excessive thirst and urination.  Ingestion of large quantities can be fatal, and there is no antidote. 
ONIONS AND GARLIC
All forms of onions and garlic can destroy a dog's red blood cells, leading to anemia. Symptoms may include vomiting, weakness, shortness of breath, dullness and lack of interest in food. 
SALT AND SALTY FOODS
Ingestion of salt and salty foods can lead to excessive thirst and urination as well as sodium ion poisoning. Symptoms include vomiting and diarrhea, depression, seizures, fever and possible death. 
GRAPES AND RAISINS
Although the reasons aren't clear, consuming even small quantities of grapes or raisins can lead to kidney failure in dogs. Vomiting, lethargy and depression or initial symptoms that dogs may exhibit after eating grapes or raisins. 
Xylitol is an ingredient that is present in many candies, gums, baked goods and toothpaste. This sweetener causes a release of insulin that can lead to liver failure. Early symptoms include vomiting, lethargy and lack of coordination, which can progress to seizures, elevated liver enzymes and liver failure within a matter of days. 
If a dog consumes yeast dough, the dough may expand and cause gas in his digestive tract, leading to bloating and discomfort. Twisting of the intestines may occur, which is a life-threatening emergency.  As the yeast ferments, it can release alcohol, leading to possible alcohol poisoning. 
PEACHES, PLUMS AND PERSIMMONS
The pit is the biggest problem when it comes to peaches, plums and persimmons. If a dog swallows the pit, it can cause inflammation obstruction in the digestive tract. In addition, the pits of plums and peaches contain cyanide, which is poisonous to dogs as well as humans. 
Other foods that aren't good for a dog include milk and dairy products and nuts, which can cause vomiting and diarrhea when dogs consume them.  Raw eggs can cause salmonella poisoning and interfere with absorption of certain B vitamins, leading to issues with the dog's skin and coat. Bones are dangerous for dogs to eat due to the danger of splintering that can lead to perforations within the digestive tract.