I am very sorry about your sister. My mom died 11 years ago from Alzheimer’s. It was kind of endearing initially, but the last month or so was absolutely horrifying. Prepare yourself.
Read/watch any number of studies (eg, search YouTube for “sugar dementia”), and you will find that the likely cause of most dementia (and heart disease and cancer and diabetes and pancreas issues and gut health issues and arthritis) is an overabundance of sugar in the diet for entire lifetimes.
So feeding an Alzheimer’s patient more sugar is, to me, akin to giving a cancer patient a pack of cigarettes, or an alcoholic a bottle of whiskey. Sure it makes them feel better in the short run, but...
My sister already died.