The other answers are correct that Smeargle can't be used in SWSH, along with Sketch being a move you can't select in battle. Through pure speculation, it can be assumed that Dynamax Cannon can be sketched. Even Smogon has inferred that, as seen in this replay. While it hasn't been confirmed that Sketch can sketch Dynamax Cannon, with Sketch not even being selectable in SWSH, if it were, Dynamax Cannon would probably be sketchable.
So, no, it can't be sketched, unless you're playing a NatDex battle on Showdown!.
Hope this helps! :)