@Becky is correct that cake poses multiple health problems for pre-diabetics and diabetics.
Coming from a family of diabetics, including a grandfather who died from diabetic complications, I can tell you the issue iis far more complex than sugar. It’s the glycemic load from carbohydrates that increase the blood glucose.
Carbohydrates have two forms:
The body can use sugar directly, but to use a starch, it must first convert it to sugar.
So removing the sugar from a baked good does not necessarily make it safe/appropriate for a pre-diabetic/diabetic to eat. If the food contains a high availabile carbohydrate starch, the pre-disbetic/diabetic is going to suffer the same increase in blood glucose as they would from eating sugar.
Pre-diabetes can be reversed with proper diet and in some cases a combination of diet and medication. So feeding a prediabetic person foods like cake is only going to cause harm as such foods are the precursors to full-blown diabetes.
The wheat flour in cake has a high glycemic index. The higher the glycemic index (GI) of a food and its carbohydrate availability, the greater the impact it will have on blood glucose levels. The GI scale goes from 0 to 100. Anything above a 50 is considered high; 70 and above is very high.
Wheat flour has a high GI of 70 or greater depending on the type of flour. It also has a high carbohydrate availability, meaning the body can metabolize more of it.
By comparison, granulated sugar has a GI of 61. So even if you remove the sugar you’re still creating a food with a high GI.
But it’s not just the GI, it’s the carbohydrates that are available for the body to metabolize. Watermelon and a donut each have a GI of 76. But the wheat starch in the donut has a considerably higher available carbohydrate, so eating the donut will have significantly more impact on glucose levels than the watermelon.
I have two siblings with diabetes, both insulin dependent. I never bake sweets for them—ever. Baked goods are full of wheat flour. Wheat flour is 80% starch. The amount of available carbohydrates makes it a blood glucose bomb.
Aside from being a carbohydrate starch bomb, gifting cake simply undermines the difficult lifelong dietary changes they must adopt to remain healthy and manage their medical condition.
Being a celiac I cannot eat wheat. So I do understand what it’s like to live with dietary restrictions. Friends who convert their favorite recipes to gluten-free put me in a very awkward position. I am not diabetic, but I am genetically predisposed to diabetes; so my glucose levels can get pretty high.
I do not want to consume those high starch gluten free flours. Yet when someone presents me with something they baked “just for me”
there is an obligation to eat it. This holds true for most people with dietary restrictions. We understand the caring behind the gesture but it does force us to eat something that isn’t good for us or risk hurting the feelings of people we care about.
Rather than look for ways to feed your favorite cake recipes to your friend I would recommend you research the diabetic diet, the role of carbohydrates in diabetes, and the glycemic index. Offering a meal or dessert that is naturally balanced on the glycemic index is far more appreciated than a sugar free cake that looks and taste nothing like real cake, and worse, still poses the same health risk as the sugar itself.
So much of life revolves around food. And there are a lot of foods that diabetics can eat without risk. Unfortunately sugar free cake is not one of those foods.
Understanding Carbohydrates
http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/
Understanding the Glycemic Index and how carbohydrates raised the blood glucose levels
https://lpi.oregonstate.edu/mic/food-beverages/glycemic-index-glycemic-load#glycemic-load