Grapes are very bad for your dog
From the ASPCA Site
Grapes and Raisins
Grapes and raisins have recently been associated with the development of kidney failure in dogs. At this time, the exact cause of the kidney failure isn’t clear, nor is it clear why some dogs can eat these fruits without harm, while others develop life-threatening problems after eating even a few grapes or raisins. Some dogs eat these fruits and experience no ill effects—but then eat them later on and become very ill. Until the cause of the toxicosis is better identified, the safest course of action is to avoid feeding grapes or raisins to your dog. Dogs experiencing grape or raisin toxicosis usually develop vomiting, lethargy or diarrhea within 12 hours of ingestion. As signs progress, dogs become increasingly lethargic and dehydrated, refuse to eat and may show a transient increase in urination followed by decreased or absent urination in later stages. Death due to kidney failure may occur within three to four days, or long-term kidney disease may persist in dogs who survive the acute intoxication. Successful treatment requires prompt veterinary treatment to maintain good urine flow
Foods That Are Hazardous to Dogs | ASPCA