A few things that comes to mind.
1. Modifying points
Have them moving an object from a to b. Move the object to a different location. Do this enough times and they'll get tired. Then show them how to use the shift function.
Make them move a object from a to b, then switch the tool to a similar but where the TCP coordinates aren't the same. Tell them that they are not allowed to modify the points.
Use a table on wheels and have the robot move a part from a to b. Move the table. Also here they aren't allowed to modify any points.
Create a slow and weird process and make them optimize the movements.