If you're out of baking powder and you're in a pinch, there are a few substitutes you can use to make your waffles. One substitute is to mix 1/4 teaspoon cream of tartar with 1/4 teaspoon baking soda. Another is to mix 1 teaspoon lemon juice or vinegar with 1/2 teaspoon baking soda. Either of these substitutes should work well in your waffles!