I'd think everything is adjustable and for a fizz, maybe drop one of those vitamin C tablets in it or maybe those potassium chloride ones I've had to take in hospital would do...

but. more seriously, I'd still think just make your "syrup". Can't really keep to the topic here but can give the elderflower cordial and blackcurrant cordial ones Pip makes here. Think they come down to "just boil some fruit juice with some sugar".