Preheat your oven to the temperature specified on the lemon loaf cake mix box. Grease and flour a loaf pan, ensuring all sides are well coated.
In a large mixing bowl, combine the lemon loaf cake mix, eggs, vegetable oil, water, and lemon juice. Mix until the batter is smooth and fully combined, about 1–2 minutes.
Transfer the batter to the prepared loaf pan and smooth the top evenly. Bake according to the package instructions, or until a toothpick inserted into the center comes out clean, about 30 minutes.
Remove the cake from the oven and let it cool in the pan for 10 minutes. Meanwhile, prepare the lemon frosting or drizzle mix according to the package instructions, whisking until smooth and free of lumps.
Carefully transfer the cake to a wire rack and let it cool completely, about 5 minutes more. Place the cake on a serving plate and spoon the lemon drizzle over the top, allowing it to drip down the sides. Let the drizzle set for a few minutes before slicing and serving.