That is an up hill battle:( I think commitment turns off a lot of kids, but you try to get something going by first presenting an interesting sport movie and then field questions from the kids about what sport would they want to try and what would help them to appreciate the fun of playing a sport. Their answers might surprise you. Playing with friends, like in the movie,The Sandlot, keeps the stress level low, but anticipation fun. Picking names for a team, have the kids recruit friends, and designing a tee shirt for their team might add to the fun of trying a sport.
First, try to make them understand the negative effects of being addicted to online games by giving them practical examples of the negative effects of being addicted to such games. Then, try to introduce sports slowly so that they do not realize that, that is what you intended. You can introduce the sports as a part time activity and bring in even their friends in order to encourage them. You have to be patient with them, because this may take time that you expect.