You can substitute yeast with equal parts acid (like vinegar or lemon juice) and baking soda. This pancake recipe calls for 2 teaspoons of yeast, so you can use 1 teaspoon of lemon juice and 1 teaspoon of baking soda. Or, you can simply use 2 teaspoons of baking powder as a substitute for yeast. Just keep in mind that baking powder activates instantly, so you'll want to start cooking the pancakes right away.