Double Battles or Trainer Battles. (Not online or Smeargle won’t keep the sketched move.) The way this works is you need to enter a double battle with a Smeargle and some other Pokémon that knows Roar or Teleport. Then, you need the Smeargle to outspeed your partner that knows Roar or Teleport, and have the Smeargle use Taunt. Then, your partner’s move will fail because they’re taunted, and then you can outspeed your partner next turn and sketch their failed move. For a much less complicated endeavor, just find a wild Pokémon lower leveled then you that knows Teleport, Roar, Whirlwind, Circle Throw, or anything like that with Smeargle in the front of your party. Then, waste a turn using any move on Smeargle. Then, their move will fail as wild Pokémon cannot faze out a Pokémon higher leveled than it. Finally, you can Sketch their failed fazing move. In short, in order to sketch a move like that, you need the user of Roar or Teleport to fail.