Whisk together the sourdough discard, water, and flour. Cover and let rest for a couple of hours (or overnight).
Add the sugar, eggs, melted butter, canola oil, and a pinch of salt to the sourdough batter and stir well until combined.
Heat the waffle iron (I love this heart-shaped waffle iron which makes thinner waffles). You don’t really need to spray the waffle iron if it has a non-stick coating and the batter contains oil and helps to prevent sticking. Use 1/3 cup of batter per waffle and bake golden brown.
Sprinkle with powdered sugar before serving.