If a dog's feet smell like popcorn, corn chips or moldy bread, the dog most likely has a yeast infection. Yeast infections are a common cause of an unpleasant odor arising from a dog's feet or ears. Dogs with a yeast infection also scratch frequently.
Dragging its hindquarters along the ground is another sign of a yeast infection in dogs. A dog who smells bad for a long period of time, or has the same unpleasant odor irregularly, should see a veterinarian for evaluation. Other possible causes of a smelly dog could be gas, rolling around in smelly objects, or a poor diet.