Preheat the oven to 250°F. Spray a 5x9-inch loaf pan with nonstick spray and set aside.

In a large bowl, combine 1 cup honey, 1 cup milk, and 1 cup firmly packed brown sugar. Beat with an electric mixer on medium speed until smooth and well blended.

In a separate bowl, whisk together 3½ cups all-purpose flour, 2 teaspoons ground cinnamon, 1 teaspoon baking soda, and ½ teaspoon salt until evenly combined.

Add the dry ingredients to the honey mixture and stir with a spatula or wooden spoon just until combined and no large streaks of flour remain; do not overmix.

Pour the batter into the prepared 5x9-inch loaf pan and smooth the top.

Bake in the preheated 250°F oven for about 3 hours, checking at 2½ hours. The bread is done when a toothpick inserted into the center comes out clean or with a few dry crumbs.

Remove the pan from the oven and place it on a wire rack. Let the bread cool in the pan 10–15 minutes, then turn it out onto the rack and cool completely before slicing.