Place the apple cider in a large pot over medium heat.

Bring the cider to a boil, then reduce the heat to a low simmer.

Cook, stirring occasionally, until the cider has reduced to about 2 cups. This takes between 3–5 hours (mine took about 4 hours).

The syrup should have the consistency of hot, runny honey—it will continue to thicken slightly as it cools.

If you used cinnamon sticks, remove them before storing.