Whilst it’s zero carb it can have an affect on BG, many report this, it’s thought that the sweet taste can trigger an insulin response in some people because the body thinks it’s getting something sweet so the pancreas throws out insulin which then triggers the liver to throw out glucose when it realises no food is coming, throw insulin resistance into the mix and its a perfect storm pushing your BG up.
Having said that some report no effects at all so the best advice is to test and see if it affects you, if the numbers are acceptable for you then it may be ok. But on another note lots of sweeteners aren’t good for anyone regardless of diabetes or not so I wouldn’t recommend “limitless” amounts for anyone. I do have a small glass of IrnBru Extra a day but just with my main meal, the rest of the time I drink water, black tea & coffee, fruit teas and electrolyte tabs once a day