The fact that Patrick Kane has a lethal shot explains why it is reasonable for him to be at his best at all times, even during practice, because he is a very good player.
In the following clip you can see footage from a past practice, where he practically undressed Fleury on the shootout, causing him to get pissed off, so that he threw his twig at him.
In order to humiliate Fleury, Kane would pick it up, acting as if he was going to give it back to him, but in the end he would just drop it when he was done, either in an attempt to humiliate him or as a joke.