Jago and Spinal both have the same command motion input for their projectiles: quarter-circle-forward + any punch. For Jago, this does an Endokuken; for Spinal, this does his Searing Skull.
Likely also possible with Sadira: Widow's Bite can be performed by doing a quarter-circle-forward + any punch while in the air. Might need to perform her double jump (up-up) and use the thumbstick to have enough time to pull off the move.
For Glacius, you'll want to perform its Hail move: quarter-circle-back + any punch.
The challenge unlocks after finishing the match, at the match results screen.