I always carry Sudafed and ibuprofen for flights (pseudoephedrine from behind the counter available in the US and UK). And I prefer juice or electrolyte drinks over water for solid hydration.

Also, just plan for a good saline sinus rinse when I get home or to a hotel. Most pharmacies have ready made saline solution that you can just shoot straight in there... fun times... alternatively, keep a sinus rinse kit with you and be prepared for local water. I've resorted to chasing down demineralised or distilled before for this purpose (and to clean out my travel nebulizer)