I've had some biggish dogs, and was advised that an appropriate punishment for pups was to put the hand under the dog's muzzle and move the dog's head swiftly (but GENTLY) upwards. Just a little bit so the angle of the dog's muzzle is elevated maybe 30 degrees. Then immediately take your hand away. Apparantly its a control thing - it shows you're in charge & they are not. It also has the virtue that the dog finds it unpleasant, but it does not hurt them at all.
It seemed to work on most occasions - but sometimes a sharp rap across the top of the muzzle was needed.