Which medicine to relieve sinus inflammation and congestion is most effective?

Depends on the cause: If your symptoms are from an infection, you may need an antibiotic. However, many of these are due to a virus and won't improve with antibiotics. If you have only had symptoms for a couple of days i would wait to see if it resolves on its own. If it has been there closer to a week, see your doctor and consider an antiobiotic. Allergies would best be treated with nasal steroids such as flonase.