I don't drink any fizzy drink that has sugar in it apart from those that have sugars naturally occurring like flavoured water, I would only drinki sugar drinks like milkshakes, supplement shakes and fruit juices because they both taste good and are nutritional, coke however isn't so thats the reason I drink Pepsi Max, diet coke, and anything thats got zero or sugar free on it. I did see that coke life uses a stevia extract as an alternative sweetener which i know is in some fruit juices but again I would not drink it if it has that small amount of sugar seeing as I drink a 2l bottle over 2 days and the guideline of drinking water is 2 litres a day, doctor and nutritionist said all forms count include milkshakes that I too am probably addicted to.
Doc did say that if u mixed sugar and water in a solution in a glass you would see a much more cloudy solution as you would if you were to see through a glass of pure water, making the point that the sugar in your blood also gets into your eyes not just putting pressure onto it but making blood clots and leaks if left untreated. As for hba1c it is just down to motivation.