For the cake: Preheat oven to 350 F (175 C) and prepare a 9 x 13 inch baking pan by lightly greasing it.
In a mixing bowl, combine the flour, baking soda, and sugar. Add in the sugar, eggs, vanilla extract and crushed pineapple. Mix until fully combined. Transfer the cake batter to the prepared baking pan and bake the cake for about 30 minutes, or until it's cooked in the middle.
For the frosting: In a saucepan, combine the butter, evaporated milk, and sugar. Cook until slightly thickened, about 5-7 minutes. Add in the walnuts and shredded coconut and mix until combined.
As soon as the cake is out of the oven, poke holes into the cake using a fork or the back of a wooden spoon. Immediately pour over the prepared frosting. Let cool, and serve.