The hot air balloon relates to Charles Law because it contains gas particles that
when they are heated they move around and make more energy than a normal
balloon.
Popping balloons in the sun is an example of the Charles Law because when they heat up in the sun they pop because of high temperature.
Exploding cans in the sun is a good example of Charles Law because when they are exposed to the sun the pressure inside the can increases and there is a point in which the pressure is too much that the volume of the can can't hold on and it results in an explosion.
When a ping pong ball is dented the best solution could be to put it in hot water. With the pressure that the hot water is creating inside the ball the dented part is popped up and is back to normal. This is an example of Charles Law because we can see how increasing temperature increases pressure.