Unlike people, chickens don't get "colds". They get respiratory diseases, some of which can be quite serious. However, your birds may not have a respiratory disease-- is it dusty in the coop? Dust, or high ammonia levels, can cause wheezing/sneezing too.
A respiratory disease is possible, though. Some common respiratory diseases are Infectious Bronchitis (which is usually relatively mild), Chronic Respiratory Disease (more severe), and Infectious Coryza (which yours probably don't have, as it usually causes severe swelling and a foul smell). My first guess would be that your chickens have Infectious Bronchitis.
If you have just noticed this sneezing, I'd isolate the sick birds. If its been going on for a while, isolating will likely make little, if any, difference, as the other birds have already been exposed to the disease.
I'd start giving your birds some elctrolytes and vitamins. This will boost their immune system and help them fight off the disease. Infectious Bronchitis is a viral diseases, which means that antibiotics won't help a lot. But, it would still be a good idea to get antibiotics in case it is a bacterial disease. Also, antibiotics can prevent secondary bacterial infections even if the birds are suffering from a viral disease.
Tyaln50 is one of the better antibiotics for respiratory diseases. It is usually given as an injection, though there is a water soluable powder version, but this is more difficult to find. You should be able to find Tylan50 at a feed store or livestock supply store. If using Tylan injectable, get some 20-22 gauge needles and syringes to give the injection.
Keep in mind that even though antibiotics may seem to "cure" your bird, and the birds may seem to recover, most respiratory diseases make birds carriers for life. These carrier birds can pass it on to other chickens, and sometimes to their own offspring through the egg.