My dog is showing symptoms of a cold, but I have been told that dogs cannot catch colds. He is sneezing and sleeping more, and seems a bit quiet. He is 3 years old. He is eating his food. Would the vet be able to do anything, or will it just be time that heals?

Dogs don't get "colds" per se, but they do get respitory infections. if you're worried then go see your vet.

However, honey and lemon both work well as antibiotics in dogs, as well as in humans, and "Buttercup Syrup", the cough mixture, is safe for dogs too. maybe try mixing some in their food? my dogs LOVE Buttercup Syrup and beg at my feet if I'm taking it myself.

DON'T self medicate your dog, take him to the vet and get a professional opinion.