One that's very easy to make is bread kvass : basically just toasted bread, sugar and some yeast, either sourdough starter or regular bread yeast. It kinda tastes like a weak wheat beer. I assume with some hops it would taste even more like beer.
I love ginger and one easy one is ginger ale. Simply boiled ginger with sugar and after it cools add baker's yeast, bottle and let it ferment a few days. I started out using wine yeasts, but after it occurred to me that it was only going to ferment for 2-3 days (after that the yeast eats all the sugar and you lose a lot of the flavor) so I just started using whatever baking yeast I had on hand.
No, I mean enzyme drink. They are called differently all over the place. They are similar to kombucha, just without all that disgusting shroom in a jar thing.
No, kvass and other 'fizzy drinks' are not kombucha
They get their fermentation from the air, ferment much lower, and do not rely on the skoby to keep it all working. On some level there is similarities, but its not the same