The highest recorded speed of a sneeze was 102 miles (165 Km) an hour. Sneezing is a natural body reaction which helps us to clear out breathing passages. Whenever we get dust or a foreign object in our nostrils, we automatically sneeze to blow the foreign body out. Some people, but not all, sneeze when they look up at the sun. Some people even sneeze when they look at a bright light. There is even a recognised name given to these people ~ the medical journal calls this process Photic Sneezing or Achoo (yes really!). In reality it is not the sun or bright light that makes people sneeze and although medical experts have theorised over this for many years, they don't really have an answer to the question, but it is possible that sun-sneezers angle their heads in such a way when they look up to the sun or a bright light, that dust is able to enter the nostrils quicker, hence causing the person to sneeze.
