Answer: smirking
/ˈsmərkiNG/
adjective
smiling in an irritatingly smug, conceited, or silly way.
"a smirking teammate offered mocking applause" (Oxford Languages)
Explanation: In my own words I would describe Smirking as a type of smiling mostly a specific type of smile for when you do something you know you shouldn't have done or if you feel guilty but also are enjoying it like when you set up a prank and it is about to unfold
Hope that help and makes sence