Note that although artificial sweeteners like stevia and erythritol don't raise the blood glucose at all and have GI index of zero or near zero - some artificial sweeteners actually do raise blood glucose, like maltitol etc, and these sweeteners are unfortunately often found in sugar-free candy. You can try a web search for "GI index artificial sweeteners" to see a list of sweeteners that have low GI score.
Something else to keep in mind is that over consumption of very carb heavy products like bread or pasta will have the exact same effect on your blood glucose as just eating sugar.