Milk is the least crucial ingredient in baking, so if you need to cut back somewhere on liquids, start here. As you become comfortable with your baking skills and more experienced, you may find that some milk substitutes are easier to work with than others. And you may learn to accommodate for shortcomings. For example, when using rice milk, I find that adding 2-3 tablespoons of extra oil helps offset the watery consistency in the dough. Eggs Most baking problems start when substituting eggs for fats.
Eggs are a challenge to substitute.
In baking, eggs provide richness, color, protein, and tenderness. When beaten, egg whites provide extra volume and air. A general rule of thumb is to look at the number of eggs required in the recipe. If the recipe calls for 1 egg, typically it serves as a binder. In this case, almost any egg substitute will work.