Best way to smash a Cube made out of 100x100x100 cubes.

I did mention in my problem that : "I only need to create as much mini cubes as I need to cover the surface". So instead of having a million cubes i would only have (100 + 90 + 90 + 90 + 90 +60? = 500 cubes). My question was/is what is the best way to add additional cubes after the surface ones are removed

You could use a particle effect, make a spritesheet with several frames of a rotating cube.

This thread used to be some sort of reference to people trying that.

Each side will be 100 x 100 cubes (give or take), so just doing the sides is around 50,000 cubes, not 500. For the explosion, you are going to have to have the surface cubes plus at least some percentage of the interior cubes. Using 50,000 is problematic. Using 150,000 or 250,000 like you'll need for a good looking explosion is unusable. I've run some Unity apps using 50,000 game objects on my desktop. They were non-moving objects with shared material and batched, and the app ran vary slowly. If you don't believe me, 15 minutes of coding should allow you to build the surface cubes, and you can test it yourself.

If you really want this to work, then you are going to have to figure out alternate solutions. Maybe a ParticleSystem. Maybe Voxles. Maybe some sort of shader magic.