As far as I know dogs usually don't get cold. Probably it might regularly come in contact with something that will block his respiratory system, because of which it sneez.
Dogs can get allergies just like humans can. It will tend to look like your dog has a cold and her eyes may start to water. If this is a reoccurring thing you should take your dog to the Vet to see if there is a larger issue at hand.
You should ask your vet about that, the vet would know what is causing it. You maybe giving the dog the cold yourself, because dogs and cats can get colds just like humans can.
There is many reasons why this might happen. One is that the dog might be in a cold area and might just have the sniffles. In that case you might want to get a dog nasal remedy to help him release the some mucus because he might have a nasal infection.
