Yes, I would love to try antibiotics, I just don't whats available without a prescription.
Good point and suggestions.Sneezing, cough/head shaking could also be caused by something in the environment such as; dust from dust bathing, mold or mildew in the coop, improper ventilation, ammonia fumes from soiled bedding, inhalation of feed dust, pollen, pesticide use.
All of these can be corrected or eliminated.
Also look inside the mouth for tiny white splotches in the back of the mouth going down the esophagus and on the roof of the mouth. This would indicate a yeast infection.
@Tacswa3, can you take a video of the sick chicken?