I'm diabetic, so I drink diet caffeine-free Pepsi.
Like you, my wonderful former father-in-law was diabetic, severely hampered by the disease (Type 1), but he loved my homemade apple pie. He would eat the tiniest sliver and pay a price ... so I figured out a way to make for him sugar-free apple pies that he was able to enjoy in much better health: I used golden delicious apples, the yellowest and sweetest I could find, and a sprinkling of yellow raisins mixed in with the applies instead of sugar. He was able to calculate his way (he paid careful attention to every morsel he ate) to eating that pie in good health for many years. I am so happy that I was able to provide him such a nice simple pleasure; he was a wonderful man.
Truly ... there are no shortcuts; fake sugar is in the long run, bad for the body. In small amounts .. heck, I drink diet soda myself on occasion. But as a daily or weekly deal ...
... you can't fool Mother Nature!