But if I respond with, "No thanks, I don't eat sugar," then it sounds like I am uppety and better-than-thou.
When I respond with a simple, "No, thank you." Then the offerer usually tries to press, "Oh come on, take one...." or they berate themselves because they don't have that kind of "will power" and so forth.
I always appreciate it when I go to a meeting or whatever and the treats are just out on a table for those who want them... rather than having someone serving and asking if I want any.
And I especially appreciate when people offer additional choices that are not full of refined sugar, like fresh fruit, or chips and salsa.
My husband, a diabetic, enjoys making people squirm. When offered treats he responds with, "What are you trying to do, kill me?" :)