I'm going to put extreme hot chilli in my sandwich to deter theft
Who is stealing your sandwiches that leads you to putting chili in it? Have you reported it to anyone?
Yes, I'm afraid of the situation when someone else will try to snatch this sandwich while I'm away. They won't like the spice.
You have every right to put anything with your sandwich, but I am afraid that the person who steals it may be very hurt in the process. If you can, try to just get surveillance evidence to properly and legally catch who is stealing the sandwiches and leave the law to decide on what will be the proper punishment.
I'm not going to care if this happens because of my chilli. Now I know I will have my sandwich by myself.
It would be better to find a way to stop the theft altogether instead of potentially hurting someone and causing legal problems. Wouldn't it be better not to have to worry about theft at all so you can have a sandwich you like?