I have been sceptical about this 'say sorry' business since I first raised an eyebrow at the idea of police giving a conditional caution that includes a letter of apology. For one thing, not too many offenders are literate or articulate, and anyone can pretend to be sorry, just as I would do when my mother told me to apologise to someone for something. A mumbled sorry, given with eyes downcast or averted doesn't mean a lot.
I had the idea of producing a pro-forma letter to save time, along the lines of
I am writing to say how sorry I am for stealing/damaging/breaking into/assaulting/swearing at you/your house/your car/your cat. I was angry/drunk/out of my skull at the time and I will try to be better in future.
I hope that you soon get the insurance money/have the stitches out/get a new cat.
All the best