I have been *exactly* where you are. I'm in charge of the kitchen snacks at work, so I have to be in there several times a day, putting out snacks, putting away snacks, re-stocking snacks...
On one of my fasts, I was clearing snacks, and there were two cookies left in a jar. Like you, my mother ingrained in me that you do not waste food. (Plus the whole "starving children in wherever" thing we grew up with)
I started to put one of those cookies in my mouth, and then I thought, "What am I? A Human Garbage Can?"
and then I replied, "No, I am not!"
and I dumped those cookies into the trash.
It only hurt a little, and I felt really good about treating myself, my body, my quest for health with the respect that I/my body/my quest deserves.
I also discovered during the course of my fasts that I AM THE MASTER OF MY EATING, MY EATING DOES NOT MASTER ME.
Even when I'm menstrual. I don't HAVE to have sweets, chocolate, whatever to soothe my hormones.
I share this to encourage you to stick to your guns... You can do it.
And if you still hesitate to throw out the donuts, put them in a public place at your work with a "Help Yourself" sign, and determine to yourself that they are NOT AN OPTION for you.