Here are the ingredients for the Sierra Trail Mix bar: Organic Brown Rice Syrup, Organic Rolled Oats, Organic Raisins, Organic Peanuts, Soy Protein Isolate, Rice Flour, Organic Cane Syrup, Organic Peanut Butter, Organic Roasted Soybeans, Organic Oat Fiber, Dried Cane Syrup, Organic Soy Flour, Unsweetened Chocolate‡, Pumpkin Seeds, Sunflower Seeds, Organic Date Paste, Sea Salt, Cocoa Butter‡, Natural Flavors, Barley Malt Extract, Sunflower Oil, Vanilla Extract, Soy Lecithin, Mixed Tocopherols (Antioxidant). ALLERGEN STATEMENT: CONTAINS SOY AND PEANUTS. MAY CONTAIN TRACES OF MILK, WHEAT, AND TREE NUTS.
You've got more concerns on your hands than the sugar, however, as raisins are present and chocolate. Both of these are known to be toxic to dogs. I doubt the chocolate is enough to cause major issues for a dog this size, but the raisins are of major concern as even a minute amount can cause acute renal failure.
More info here: http://veterinarymedicine.dvm360.com/raisins-and-grapes-potentially-lethal-treats-dogs
I would recommend inducing vomiting if the consumption happened in the last 2 hours following these instructions and using a FRESH bottle of hydrogen peroxide: http://www.sunrisepetclinicaz.com/vomiting.html
It would also be wise to have your companion examined by a vet this evening and to get baseline blood work run now and a recheck a few days in the future to be sure that renal problems weren't caused by the ingestion. Some vet clinics will recommend overnight hospitalization on IV fluids following such an ingestion. If you cannot get him to vomit promptly or at home, take him to an ER this evening and allow them to do this.
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