Be careful what you buy. I didn't research this properly and bought myself diet coke, it knocked me out of ketosis when I had done six days of CD in July. I ended up coming off the diet as the hunger was unbearable and I could not work out why I was so ravenous. It took me several weeks to find the right state of mind to get back on the diet.
Some people are "lucky" and can drink this stuff without problems. The drink itself may not knock you out of ketosis, but apparently the flavourings can cause "cravings", and these will play havoc with your mind if they happen, and it is the result of giving into them that will knock you out of ketosis. This, I believe, is why CD say no to these drinks.
If you think you are one of the "lucky" ones then risk it if you feel you need something like that, but just be aware that if you start to suffer more from cravings then get the hell away from the stuff as fast as you can.
I used to be a fizzy addict, but 95% of the time I steer clear now and make my own with SF juice and sparkling water and such like. Note, I am not SS, SS+ or anything like - just calorie counting at the moment!
me personally, i wouldnt go near it...there is plenty of time post CD for those drinks...and i wouldnt want any way of blaming myself for slow losses if they occured in terms of not sticking to the rules (ok ok, the chocolates were a one off!!! lol)
But on the other hand, if its coke zero, or falling off the wagon completely, i would recommend the coke. I know some people only feel they can do the diet if they have this and so be it.
its a personal choice at the end of the day...but "officially"....its a no no!
The difference between diet coke and coke zero is that diet coke has citric acid and coke zero has malic acid. Citric acid can kick you out of ketosis. Malic acid won't. But I find that coke zero makes me really hungry, rumbly tummy etc, even though I'm still in ketosis, so although I enjoy it as i'm drinking it, I know it's not worth it cos I'll feel ravenous afterwards.