The idea consists on two steps reinforce the cable and make it stronger. We get the first one by applying a heat shrinkable (is just a little plastic tube that get smaller with heat). So for this you pass trough a small heat shrinkable up to the usb part and another one for the micro usb/ iphone connector. Then you slighly heat it with a candle and you will see how it starts getting tight.
And to make it even stronger I pass through a pen spring. I opened one of the curl and started twisting around the cable. So far no more cables broken for me!