Mountain Dew Cake

INGREDIENTS
1 (18.25 ounce) package lemon cake mix
1 (3.4 ounce) package instant vanilla pudding mix
1 cup vegetable oil
4 eggs, beaten
10 fluid ounces Mountain Dew
1 (20 ounce) can crushed pineapple with juice
1 cup white sugar
3 tablespoons cornstarch
1/4 cup butter
1 cup flaked coconut

DIRECTIONS
Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a large bowl, combine cake mix, pudding mix, oil, eggs and citrus soda. Mix until all ingredients are moistened.
Pour into prepared 9x13 inch pan and bake at 350 degrees F (175 degrees C) for 30 to 35 minutes. Cool completely.
To make the topping: In a saucepan, combine pineapple (with juice), sugar and corn starch. Bring to a boil and cook, stirring constantly, until thick. Remove from heat. Add butter and coconut. Spread topping evenly over cake