Preheat the oven to 325°F. Thoroughly grease a Bundt pan with nonstick cooking spray, then lightly dust it with flour to help the cake release easily.
In a large mixing bowl, combine 1 box yellow cake mix, 1 (4-ounce) box instant lemon pudding mix, 3/4 cup 7UP, 3/4 cup vegetable oil, and 4 large eggs.
Beat the ingredients with a hand mixer until smooth and well combined, scraping down the sides of the bowl as needed. Do not overmix.
Pour the batter evenly into the prepared Bundt pan.
Bake for 45 to 55 minutes, or until a toothpick inserted into the thickest part of the cake comes out clean or with a few moist crumbs.
Let the cake cool in the pan for 10 minutes. Carefully invert the cake onto a wire rack and let it cool completely.
Make the glaze while the cake cools. In a small bowl, whisk together 2 cups powdered sugar, 1 tablespoon fresh lemon juice, and 1 tablespoon milk until smooth. Add a small amount of additional milk if needed to reach your desired drizzling consistency.
Once the cake is completely cool, drizzle the glaze evenly over the top, allowing it to run down the sides.
Let the glaze set for a few minutes before slicing and serving.