Preheat oven to 350°F. Grease and flour two large (9 by 5-inch) loaf pans.
In a large bowl, whisk together the flour, baking soda, salt, and pumpkin pie spice. In another large bowl, use a mixer to blend together the pumpkin puree, sugar, oil, water, eggs, and vanilla until well incorporated. Slowly add in the flour mixture, stirring until just blended.
In a small bowl, stir together the sugar and cinnamon until well combined.
Divide three-quarters of the batter between the prepared pans. Sprinkle with about three-quarters of the cinnamon sugar, and use a butter knife to swirl through each loaf. Dividing the remaining batter between the pans, and sprinkle with the remaining cinnamon sugar mixture.
Bake for 60 to 65 minutes, or until a toothpick inserted in the center comes out clean. Cool bread in pans for 5 to 10 minutes and then carefully turn out onto a wire rack to cool completely.