Preheat oven to 350 degrees.
Grease or spray 1 8 x 4 loaf pan.
In a medium bowl, shift together flour, baking powder, baking soda, and salt.
In another bowl, add applesauce, sugar, pineapple guava, and egg. Mix together well.
Add wet mixture to dry mixture and stir until all is mixed in well.
Pour into loaf pan and smooth top.
Bake for 50 to 60 minutes, until toothpick inserted in comes out clean.
Remove from oven and cool in pan for 10 minutes.
Invert on to cooling rack and let cool almost completely.
Mix powdered sugar, milk, and vanilla until smooth.
Drizzle over the top of bread.
Let cool completely, slice, and eat.