Since obviously I can't just pop to the shops for a bottle here, I decided to take a crack at fermenting my own sima.
A friend provided a recipe, which I only slightly tweaked, and it's been fermenting away for like 3 days now.
It smells like ... well, it smells like a few nasty cocktail hangovers I had in my youth, to be honest. Strongly lemony, with a distinctly bilious overtone.
On tasting though, it's more pleasant, a sort of fizzy, very slightly boozy lemonade. It doesn't really hit the same notes as the simas I've had from shops and so forth, but it's not bad.