I can't personally vouch for any of these recipes because I haven't tried them, but here are some that come up in the EYB online library for vegan baking using agave nectar. There could be a small amount of sugar hidden in the "store-cupboard ingredients" but typically a healthier recipe made with agave is less likely to also have sugar.
And here's another search for baking with agave nectar, but instead of using the vegan filter, I excluded all meat and dairy/eggs. Again, there's a chance there could be a small amount of butter/milk/sugar hidden in the "store-cupboard ingredients," but this might give you a few more options to choose from.
You could also try a similar search on your own bookshelf using the same filters I used in these searches.