Dogs, just like people, do occasionally sneeze which is normal and shouldn't be a cause for concern. However if your dog is sneezing very frequently or persistently then it would be a good idea to see your vet. They can perform a thorough clinical examination.
A sneeze is essentially a normal reflex to clear the nasal passages of any irritant particles. A dog’s nose is quite sensitive and can be irritated by a number of things such as dust, pollen, certain household sprays and perfumes. Brachycephalic (short faced) breeds like French Bulldogs and Pugs may be more prone to sneezing from mild irritation, as their nasal passages are very condensed.