I did look up “how to salvage this” and saw that you can make a 1:1 sugar syrup and pour it over the cake or bread, and it should be okay as long as you don’t overdo it. Has anyone else used this trick, successfully or otherwise?
I’m planning to take it to a gathering on Tuesday.
I’ve definitely forgotten to add sugar to various things before, but soaking it in simple syrup is an ingenious solution I’ve never heard of before! It seems like it could work, though - it puts me in mind of how a number of dense cakes are made.
What are the other ingredients? Any chance you can just leave it as is and call it keto or something?
Only if I want people to eat it. It just plain old does not taste good.
Keto sweets contain things like stevia or (sometimes) agave nectar, instead of sugar, molasses, honey, etc.
I’d certainly give it a try. You probably can’t eat it as is, pleasurably, and all it’ll cost is a few minutes to boil the water and stir in the sugar. I’d try however much sugar the recipe called for and an equal amount of water, plus I’d use a skewer or something to make a bunch of holes in the cake so that the syrup has a better chance of penetrating evenly all the way through the cake.
If you don’t want to risk it, you can bake a new one. Then use the first at home, by serving slices of the cake and pouring something sweet over the top of the slices. Like vanilla pudding. Or how about thinning some strawberry preserves down with enough water to make them pourable. I think strawberry/banana/chocolate cake sounds yummy.
Hmm–I’d be really interested in the syrup trick, but I would keep this as a home experiment. Is there something else you can make or buy for the gathering?
I’ve soaked a lemon cake in lemon syrup, but even then the cake’s already sweet.
The instructions did say to use a utensil to poke holes in it so the syrup would penetrate.
Now I’m having visions of chocolate banana trifle based on the sugarless chocolate banana bread. Or bread pudding.
I have a recipe where I put lemon juice with a little bit of sugar on the cake, but immediately after taking the cake out of the oven. The cake already has sweetness and the liquid is for boosting the moistness
If you want to wow the people at the gathering, I’d probably make something else. But it doesn’t hurt to try salvaging what you have.
I’d eat it, as is. Send it to me. 
I once used salt instead of sugar when making a lemon meringue pie. It wasn’t discovered until after the pie was out of the oven, cooled, and we took our first bite. Usually I eat some of the lemon filling when cooking, but that time I didn’t taste it until it was too late.
It’s a casual gathering, and impressing the other attendees is not something we do. I actually made it a couple weeks ago and have had it in the freezer, minus a slice, and I think I’ll thaw it, “sugar” it, and slice it further and take it with me.
Thanks, everybody!
I have no advice to help on recovery (sorry).
Out of curiosity, did you make this chocolate banana bread? (I ask because I have been considering it):
Unless I were really pressed for time, this is what I’d do, because knowing that you can experiment with the first batch, sans worrying about how it will taste to others, seems like the best option. You could do the poke-holes-and-add-simple-syrup option, or make a bread pudding, or a trifle, or use it for grilled cheese sandwiches, or — whatever, as long as you are at home and can afford to fail.
ETA: Seems relevant to mention that I once made a luscious gingerbread, but instead of a cup of sugar used a cup of salt. (I tend to buy in bulk and put ingredients into generic canisters - usually well-labeled, but obvious not in this case.)
There was no saving THAT concoction.
ETA: I would be surprised if there was a reasonable recovery of such a recipe when missing a basic ingredient. I might be wrong though.
I’d think it would be best to just make a new batch (and probably no more work than trying to fix the un-fixable).
Since it already has a slice out of it, I’d go ahead and do it, then try a piece and see if it worked.
Personally, I would suspect that, if it didn’t work on its own, you could add icing and stuff to make it work. Make it seem like the inside is deliberately less sweet to counter the icing.
The other alternative I can think of is to basically break it up and use it to make a bread pudding type desert. Go heavy on the syrup for the added liquid. If you can make bread sweet that way, surely you can also do so for cake.
How much sugar was required? With the chocolate and banana it may be sweet enough?
My host for Thanksgiving this year forgot the brown sugar in the pumpkin pie. It was definitely missing something as-is, but maple syrup (or rather, that grocery-store stuff that mimics maple syrup) poured over the top worked reasonably well.
If all else fails, soak the sliced bread in sherry and use it as the base for trifle. Everything else on top of it will be sweet enough, and the alcohol should make anyone not care if it isn’t.
My first advice follows most of the thread - do any of the above ‘fixes’ and enjoy yourself, while making a new one to share.
My second is a variant above. Especially if it’s near-frozen, it should slice well - slice really thin, and serve on a plate after soaking in an boozy syrup (brandy, rum, etc). Top with sifted powdered sugar and it’ll look elegant, or with whipped cream (I’ll judge you if you use Cool Whip but not if you use Reddi-whip) with sifted (good) cocoa powder if you rather (this doubles up on the chocolate theme).
It’ll look elegant (although the plating would be more work) and fancy, rather than a fix. 
Fantastic idea, dude! I’m contemplating making a pound cake recipe, decreasing the sugar a bit, then cubing the loaf and making bread pudding.