The key to keeping coconut strawberry cake from becoming soggy is largely about when you serve it. A cake which is baked and served on the same day won't have time to get soggy. However, just because you won't eat the whole thing immediately doesn't mean it will get a soggy texture. First, ensure the layers are completely cool before adding frosting and berries. Another method is to add a thin layer of jam or jelly before adding the frosting.