If you're targeting those kinds of users, connect a Sphere_Map node to the Reflection Background input, which should be set to white. To the Sphere_Map, connect an Image_Map. Provide something like an EnvSphere image, but much smaller in that Image_Map. It doesn't have to be big or good. Just has to have some vague impression of the lighting patterns found in an EnvSphere image, such as sky and ground, or a wide-angle indoor shot with floor, ceiling, windows, etc. Doesn't even have to be equirectangular. Any photo with a clear division at the midline, and with some sort of hot spots here and there will work as a source of environmental reflections.

For those using it with a true 360 env, this will have no impact at all.
 

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)