I once made a cake with no wheat flour, no sugar, no butter, and no egg, because I had to make a birthday cake for someone that couldn't eat anything with those things in it and it was an interesting challenge. It worked well enough to serve its purpose and it was edible in a surprisingly not terrible way, but I don't recommend it, better off making a "cake" out of carved fruit. I don't have the recipe anymore, but it was pretty much just a normal cake with everything substituted: rice flour instead of wheat flour with extra baking soda, an artificial sugar product suitable for baking, canola oil instead of butter, and an egg substitute product suitable for baking which I think the name of was something like "No Egg".
Don't fall for the nonsense that gluten free is healthier, it's not, unless you have celiacs disease. People with celiacs can't eat gluten as it because triggers their immune system to attack their intestinal tract, which in the long run can destroy their intestinal system which can lead to malnutrition and eventually death, so it's not good for them; but gluten is perfectly healthy and good to have in one's diet for everyone that doesn't have celiacs.
Honey, maple syrup, golden syrup, treacle, molasses, HFCS, etc; they all work to sweeten things because they all contain the same stuff: fructose and sucrose, which is what makes them sweet. The only difference between them and sugar is they also have some other stuff in them which is what makes the flavours different. So, substituting one for another isn't going to make anything more healthy, except for the bank accounts of people that push for using a particular product they have a vested interest in.
Don't let anyone fool you into thinking honey is a natural anti-biotic, it doesn't work like that. It only functions in so far as to stop the honey itself becoming infected, eating it does nothing more than give us a little sugar rush.
So, unless you're use artificial sweeteners, you're not going to get any better health outcomes by swapping sugar for something else, as nothing is sweeter than pure sugar.
That being said, making something strongly fruit flavoured can result in needing less sugar because people expect baked sweets to taste sweet, but if they taste fruity, they can be less sweet and still be very tasty because people love fruit flavoured things and fruit is also a little tart and not as sweet as sugary treats, so people will accept the item being less sweet. It's a weird little psychological trait - expectation plays a huge role in whether or not something tastes good to us. Just be aware that fruit and fruit flavourings also contain sugar, which is what makes them sweet, but you might be able to get away with using no sugar products at all if you use enough fruit or dried fruit or fruit extract flavouring.
Other sweet options that still contain sugars but can be used to sweeten foods well whilst adding another fruity or similar flavour that lets you get away with using little to no sugar include pumpkin, sweet potato, carrot, and raw sugar cane juice.
If you're a baker you should already know this, but just in case, use duck eggs instead of chicken eggs if you can get them. Higher protein and many other good stuffs, makes for a much fluffier and richer baked everything, and people that are allergic to chicken eggs can often eat duck eggs, so people that normally can't eat baked goods due to egg allergy can often do so if the baking is done with duck eggs instead [disclaimer: seek medical advice and have an epipen handy if allergic to chicken eggs when trying duck egg for the first time, because everyone is different because biology is complex].
As for making things healthier in a nutrient dense sense, again, look at fruit and veg, see what you can do with them. Also, for those that don't have nut allergies, nuts are dense in proteins and other good stuff, so nuts in baked goods do well. Wholemeal, wholegrains, good fibre which is a much needed thing in most people's diet. Less salt if you can get away with doing so might be a good thing too, though I know salt is needed for most baked things to get the texture right and it does enhance flavour.
Maybe find a new way to improve fruit cake? A lot of people don't like fruit cake, but it's one of the most healthy, nutrient dense baked goods ever invented. In Australia, a classic fruit cake recipe that was once extremely popular used a lot of pineapple in it, which made it taste lighter, fruitier, tropical, and sweeter than traditional British fruit cakes which can be somewhat bitter.
