Speech sound practise should be fun!
Make sure it’s a sound they can actually say but they just need practice to use more often. Briefly pause any game to build anticipation, then have them imitate you. This increases motivation as they want the game to continue. Then you can keep the activity going after their attempt.
If what they’ve said isn’t quite right, you can give specific feedback and try again later. “I can see you’re trying hard to get that sound! It’s tricky!”
Watch me model this with Auggie on the swings here