Drilled holes in mini fridge. Do I.......?

So once I drill the holes so that my heat tape cord pops out to the back, do I fill the hole or cover it? If so with what?

I'd fill it with some expanding foam insulation. It costs about $5 a can at home depot/lowes/etc..

I do both, I filled the drain plug (through which my cable go through) with play-doh and covered it with foil tape.

This way it's not permanent (should you make some changes) however it's air tight.

Those are both great ideas guys. Thanks