Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or spray with nonstick spray.
Make the cake batter:In a large bowl, whisk together the cake mix, eggs, sour cream (or yogurt), oil, milk, and vanilla extract until smooth.
Make the cinnamon swirl:In a small bowl, mix together the brown sugar and cinnamon.
Layer it up:Pour half of the batter into the pan and spread evenly. Sprinkle the cinnamon-sugar mixture evenly over the batter.Pour the remaining batter over top and gently swirl the layers with a butter knife—don’t overdo it!
Bake:Bake for 35–40 minutes, or until a toothpick inserted in the center comes out clean and the top is golden.
Glaze it up:While the cake is still warm (not hot), whisk together powdered sugar, milk, vanilla, and honey until smooth.Pour the glaze over the warm cake and let it soak in as it cools.
Cool slightly before slicing. Serve warm or at room temp—both are delish.