This well randomly generate a bad dad joke
!command add !dadjoke ${customapi.https://api.scorpstuff.com/dadjokes.php}
!command add !dadjoke ${customapi.https://api.scorpstuff.com/dadjokes.php}
If you add the command in StreamElements is should look like this
!command edit !dadjoke ${customapi.https://icanhazdadjoke.com/nightbot}