It's very hard to find recipes for tangerine sorbet without the sugar. My best suggestion for you, as long as you do not want sugar in it, replace the sugar with a sugar substitute, an artificial sweetener, or even try adding honey to the recipe, and you'll add some sweetness to it.

I have not tried these recipes, yet they seem like they are just what you're looking for:

Rosemary and Honey Oranges with Tangerine Sorbet
http://www.bigoven.com/130078-Rosemary-And-Honey-Oranges-with-Tangerine-Sorbet-recipe.html

Tangerine Sorbet
http://fxcuisine.com/Default.asp?language=2&Display=163&resolution=high&page=2

I used to do this all the time when I was a kid, yummy and healthy, If you do not want any sugar or dairy then you probably don't want honey since that is basically sugar, I used to add vanilla extract it gave it a slight hint of those creamsicles, no need for complicated equipment, just squeeze tangerines, add vanilla and freeze, this is so simple and it is so good!, If you want to make it one step more complicated, as it just starts to freeze stir it up, then stir it up every 15 minutes, this kind of gives it a more sorbet texture but you really can just freeze it and eat it. I remember putting this on toaster waffles in the morning when I was a kid, there is something magical about the combination of vanilla extract and tangerine. Enjoy!

PS. No need to use water. if it is too sweet then use a little club soda to dillute it will also give it a fluffier texture

Tangerine Sorbet

Juice of 5 large tangerine
2Tbs honey
Juice of 1 lemon
1 Tbs Tangerine zest,
minced 2 tsp Lemon zest,
minced 1/4 cup fresh mint,
finely chopped 1/4 cup fresh basil,

finely chopped In a small saucepan, combine 1/2 cup of the tangerine juice and honey. Let simmer for 4-5 minutes until honey is melted. Remove from heat. Add remaining ingredients, stir together and place in the refrigerator to chill. Once chilled, place mixture in your favorite ice cream maker and process. Return to freezer until ready to serve.

This recipe uses honey (fructose) instead of sugar.

INGREDIENTS
1 ltangerine's peel, finely diced
1 cup water
1/2 cup sugar
1/2 cup tangerine juice
1/2 cup carbonated mineral water
6 strips of tangerine zest, for garnish

DIRECTIONS
In a saucepan, stir together the diced tangerine peel, 1 cup of water and sugar. Bring to a boil, then reduce heat to medium and simmer for 5 minutes. Remove from the heat, and allow to cool.
In a pitcher or bowl, stir together the tangerine syrup with peel, tangerine juice and mineral water. Pour into an ice cream maker, and freeze according to the manufacturer's instructions. Garnish each serving with a twist of tangerine peel.
If you do not have an ice cream maker, you may freeze it in a tall canister. Freeze for 1 1/2 hours. Remove and stir with a whisk. Return to the freezer and stir about once every hour for about 4 hours. The more times you stir, the more air will be incorporated, resulting in a lighter finished product.

http://images.allrecipes.com/site/allrecipes/area/community/userphoto/big/15497.jpg