Add the cranberries to a small saucepan.
Zest the mandarins, and add it to the saucepan. Squeeze the juice into the saucepan as well, catching bits of the flesh too as you do. It will all blend into the sauce.
Add the remaining ingredients. If the cinnamon stick is long, you can break it into two or three pieces so that they are all submerged.
Stir together, and bring to a boil at a medium-high setting, stirring occasionally.
Keep at a boil, stirring constantly as it thickens.
Let it simmer for 3 to 5 minutes, and then remove from the heat.
Remove the cinnamon sticks, and allow it to cool.
Use as desired.
It will keep in the fridge, covered, for about a week.