The Flash Strips don't have any carbs or sugar alcohols. Those are the little thin strips that melt in your mouth. They're quite intense, but they really help ketosis breath.

I have been chewing sugar free gum. I just look for the lowest amount of carbs, and subtract the sugar alcohols. Usually it amounts to 2 grams of carbs, and 2 grams of sugar alcohols, equaling 0 (zero) effective carbs. It hasn't caused me to stall, and I am a big fan of gum.
I'm quite new at this, but haven't had any trouble with sugarless gum.