I feel like it might be an east coast thing. I know that movie takes place on the east coast, and my friend from Boston has always said “sack”. Has anyone else noticed this?
I am an easterner,and one of my nephews (Ben’s first cousin) is Zachery, called Zach and pronounced Zack. I have never heard anyone say “sack.” Does your friend have a speech impediment : -)
Here’s another idea: in espanol the letter “z” is pronounced like an “s”. Maybe all the
people who are disgusting you are native spanish speakers. Though I doubt it.