MW Windows and Doors provides a cleaning and maintenance guide for vinyl windows. Alternatively, check with the vinyl window manufacturer for their recommendations to clean the window.
Cleaning vinyl windows varies little from other windows with one exception. Never use abrasive scrubbers or substances, as abrasives will mar the surface of the vinyl, as MW Windows and Doors notes. A low-pressure spray with the garden hose, working from the top down and pointed indirectly at the window, is often enough to clean the exterior. Inside, try using a water-based cleanser, such as Windex, Lysol or Fantastik.