Fermented fruits for ducks: how much alcohol can they stand?

Free feed usually come in batches: leftovers from a harvest for example. If there in huge amounts, it is usually wasted.
To preserve food, fermentation is used. Either lacto-fermentation (with low-sugar substrate), or alcoholic fermentation (with high-sugar substrate).

When having too much fruit, it could be fermented, stored, and fed to ducks. But how much alcohol can they thrive on? In nature, many animals get drunk on alcohol, as a quick video search on the net shows. Therefore they are able to process at least part of it.

But how much? Does one of you do this?

I found this article which describes trials with alcohol in drinking water for ducks, but as ducks drink quite a lot, I imagine it is worse than having the alcohol in the feed.

Especially table 2 is interesting:
https://sci-hub.st/https://doi.org/10.1159/000175313

Have to admit i didn't make much sense of that paper but damn do i love forums,  ask a question and get an answer like, here's a  scientist that got ducks drunk for science hahaha

Are the ducks getting a 'wobble' in their 'wattle"?

I have tried to feed my birds sauerkraut, and they refused to eat it.

I have definitely heard of goats hoovering mash leftover from beer making and getting drunk on it if given too much.

I have not tried to ferment our extra fruit specifically for either my ducks or chickens. Alcohol is a poison depending on the amount vs body weight, so I would experiment with caution. It certainly is a shame to waste piles of fruit, but I figure to some degree it is feeding the soil, even if it's not feeding my animals.