Combine apples and sugar in a medium bowl, allowing them to sit for approximately 30 minutes.
To get started, preheat your oven to 350°F (175°C) and prepare two 10x15-inch baking pans by greasing and flouring them.
Begin by stirring water into the bowl containing apples. In a separate small bowl, blend together eggs and margarine, then incorporate this mixture into the apples. Next, combine the flour, baking soda, cinnamon, and salt, followed by the addition of raisins and walnuts. Finally, transfer the resulting mixture into the prepared pans.
In the preheated oven, bake for one hour or until a toothpick inserted in the center comes out clean. Allow it to cool briefly before removing it from the pans.
Combine powdered sugar, hot water, and vanilla extract in a medium bowl. Then, drizzle this mixture over the warm cakes.