Never heard of it, only banana beer (which is made in a different region) but I imagine it wouldn't be hard to make. You can get flaked corn, and I think even malted corn; malted sorghum I dunno, but sorghum extract is available. You could go with wild fermentation following a sour mash, but given the cost of getting sorghum extract or malt here, I'm guessing I'd probably go with a lacto and wild yeast inoculation concurrent to some basic, aggressive yeast. (I'm guessing bread yeast is common.)
She told me that the taste of it is quite sour, but I should've asked her if it was carbonated, or how much and what the color is. A little more research is due, I guess.
Yeah, looks like it's a two day sour mash, and without airlocks and stuff, so likely quite sour.
From the instructions here (which may or may not be at all reliable) I'm thinking it's probably bubbly because there's still ongoing fermentation (sort of like dong-dong-ju, or fresh makkeoli).
I've also seen some very interesting Banana Beer (Mbele) recipes... from other regions of Africa, IIRC, but supposedly wonderful, and similarly drunk young and sweet, while still fizzing with yeast fermentation activity.