As this video from youtuber Lifehacker & Experimenter demonstrates, just put on a kettle and boil some water. Place the ping pong ball in a glass, pour the boiling water over it, and the heat will force the material back into shape.
You can fish it out with a fork or just grab it with your fingers if you’re careful. And if you have a bunch to fix, you can do the same thing with a pot of simmering water, or just use them every time you sous video. Now your table tennis match or epic game of beer pong can continue.