This was the afternoon, I got myself a mug and filled it with coca cola. I was drinking it by the handle. In the window, I saw my sister was gonna enter the house. So like any other sane person, I stood at the middle of the living room. Just staring at the door while drinking Coke from my mug like it was coffee. It wasn't like an intense stare but a stare of pondering, wether or not I should update my story or do school work. When she entered, she didn't notice me at first but as she was closing the door she noticed and jumped. The thing she was carrying with her took off in the air and landed safely on the couch, it was food so no worries.
Tldr: I startled my sister by staring at the door while drinking Coke from a coffee mug.