Au-wide it is called soft drink.
Down here in the south (Melbourne) we also used to call it "lemonade". That is NOT just a lemon drink, but a generic term for fizzy drinks. So you had raspberry lemonade, lime lemonade, passionfruit lemonade and so on. The local brand equivalents of Seven-Up were called "plain lemonade".
The main brands were Leed lemonade (only plain and lemon flavours); Tarax, the market leader; and Marchants, my favourite as they had a special bottle with the screw thread on the INSIDE of the bottle, and a big red stopper with a grey rubber seal which screwed into the top of the bottle.
There were also a couple of home-delivered brands, including Loys and Noddys, which just called them "aerated waters".
"Spark-a-lark-a-lark-a-ling, Marchant's Lemonade!"
With a jingle like that, it's no wonder Marchants have disappeared.
Chris.