Skyrocket

Throw a fast sleeper.  While the yo-yo is spinning down at the end of the string, take the string off your finger and give a good tug.  The yo-yo will start coming back up toward your hand.  Let go of the string just before the yo-yo smacks you in the knuckles, and it will shoot up into the air.  The height that it flies depends on how fast the yo-yo is spinning, and how good your timing is on the release.  This trick will not work with unresponsive yo-yos.