My rear, top break light rattles to hell when my sub hits. Does anyone have a fix?

 

I'm assuming by top brake light you mean 3rd brake light. If so all I did was added lots of strips of dynamat xtreme inside the light to give it some resistance to not hit the window. It still vibrates a tiny bit when the system is fully up but then and only then. Due to the design of the light there's not much else you could do.

One thing I did think of was taking small washers and moving it away from the window a tad bit (would look wierd if you didn't have tint).