The traditional still was also a sort of ceramic pot still, course that wouldnt give you a particularly high abv, unlike the 95%ish abv stuff they use in the production of modern soju
And well, sweet potatoes have been in use for the longest as alternate starch sources but really traditional soju of course is just rice

Japanese schochu is still mostly produced using a pot still, though it can also have stuff like barley and sweet potatoes added in
But hey, at least its not just sweetened and watered down 95% neutral alcohol

Not that ive ever had the jap booze though

What a noble deed

Onion Whiskey

Onions contain about 4.5g of sugar per 100g from what i can find online
600lbs are 272kg, which has a total sugar content of roughly 12.25kg of sugar
which means you could ferment and distill it to get a theoretical yield of 15L of booze at 40% ABV