Licorice, cinnamon, and stevia taste sweet, but don't have sugar(i am talking about just the herbs, not some products made with these which might have added sugar).

"Second, licorice root is fifty times sweeter than sugar and has no calories."

http://locus1.com/fdr/aph/inglicorice.htm

Cinnamon

http://www.calorie-count.com/calories/item/2010.html