the Indian Premier League (IPL) seasons held outside India, the record for the fastest half-century is held by Adam Gilchrist. Representing the Deccan Chargers during the 2009 IPL season in South Africa, Gilchrist reached his fifty in just 17 balls during the semi-final against the Delhi Daredevils (now Delhi Capitals) on May 22, 2009. This explosive innings was instrumental in propelling the Deccan Chargers into the final, which they subsequently won. Wikipedia
While there have been other rapid fifties in IPL history, Gilchrist's 17-ball effort remains the quickest in IPL matches hosted outside India.