A great way to not need to add sugar or reduce sugar in baked goods is to use fruit. When fruit is ripe there is really no need to go on sweetening it, especially if you have a bit of dried fruit too.
From talking to parents I find that so many get really het up on what they should do if a child refuses part of their meal or holds out for dessert. I think you have to do the thing which works for you but I'd also advocate making sure the meal is pretty balanced anyway, e.g. having fruit as a dessert or choosing a no added sugar option rather than a sticky cake or chocolate.
Anyway, it's the way I've always approached it and from my sample of one I now have a pretty open minded toddler when it comes to food who was asking for more broccoli yesterday but saying "no" to sweet potato. Fair enough, I just go with it. I sometimes feel like kids are born with personalities and my son has definitely inherited my stubborn streak. There are times when I stand my ground but if I don't allow him some control and choices in his food, he digs his heels in and it gets worse. Likewise though just because he's refused something once, doesn't mean he won't be offered it again. This only reinforces fussy behaviour in my opinion.
A great way to get kids trying something they think they don't like is to change the way you offer it, so perhaps mashed sweet potato next time rather than roasted? He went off broccoli for a while so I used to give him
broccoli nuggets and well he's now back to loving it.
So if you do have a fussy child, don't give up, don't stop trying but do make lovely little things like these mini apple pies. Not only will your child probably wolf them down but also parents think they're pretty good too!