How To Make Strawberry Box Cake Moist. Another fun swap is to use soda pop instead of water. Another fun swap is to use soda pop instead of water.
To get an extra rich and moist cake, stir in two extra egg yolks along with the eggs the recipe calls for (save the egg whites to make these delicious meringues). For example, if making a strawberry cake, simply use strawberry soda pop for the liquid instead of what the box calls for. For my boxed cake, that meant having about a stick and a half of butter in it.