At the beginning of day 2, you have a choice: prank Bruce (in the cafeteria), or tell Ms Sugar about the plan. (She's in the main hallway.) You can only do one or the other, but you can save before you do either one. After you make your decision and get the achievement, you can reload and choose the other choice.
Note that your friends are telling you to not prank Bruce, and you need to make them all happy for another achievement.