Question: what is the best over the counter medicine for a sinus infection?
Answer: Decongestants. These work by narrowing blood vessels to help reduce inflammation and swelling that cause sinus congestion. ... 
Pain relievers. Pain caused by pressure buildup in the sinus cavities may be relieved by pain relievers such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others).