I personally haven't dealt with any respiratory problems in my poults, so I can't advise any treatments. Providing good ventilation is very important to poultry. Are they confined too tightly? What temperature is your brooder?
What kind of wood chips? How often is the sneezing? Sometimes young toms will start making a sound that sounds like sneezing but is actually a noise made when the adults display.
Do you see any discharge or hear any wheezing?