Use the Reflection shader to produce reflections from object to scene, scene to object, and object to object.

Live Planar Reflection shader effect

When a Reflection shader is appended to an object, a map or live reflection plane is generated. Sphere or Spherical reflections are mapped, and Live Planar or Live Planar On Video reflections are generated in real time.

A new map should be generated whenever you want to save adjustments made to the Reflection settings of a selected object.