I would avoid if it's got aspartame in it but I don't know if it has. Pre- Atkins I used to drink this all the time. I now drink fizzy mineral water to get the fizzyness that you are talking about, it does help curb the craving. Sometimes I put a few drops of Lime juice in it to give some flavour. I don't drink tea or coffee so this is what I drink all the time.
I didn't know that citric acid can make you come out of Ketosis how does this happen? Last week when I was drinking diet lemonade (without aspartame) but with citric acid I wasn't losing weight, maybe this was why! But the Ketostix said I was still in Ketosis though. I'm glad you mentioned it I will look out for in the future.