How to display text on a cube and how to change it dynamically?

Paste (child) a 3DText over it. Change it the usual way for 3DText (also called TextMeshes.)

The other way, changing the cube texture itself, would be a huge pain. Have to fix the unwrap (the Unity cube assigns entire texture to each face,) and so on.

Old post but I thought others might get helped by my finding: