Make the buttermilk. In a measuring cup, combine the plant-based milk and vinegar. Stir briefly and set aside for 5-10 minutes to curdle.
Preheat the waffle maker according to the manufacturer's instructions.
Mix the dry ingredients in a medium bowl. Whisk together the flour, baking soda, salt, and sugar.
Add wet ingredients by pouring the plant-based buttermilk and vanilla into the dry ingredients. Stir until just combined; do not overmix.
Cook the waffles by lightly spraying the waffle maker with cooking spray. Use a ⅓ cup measuring cup to pour batter into the waffle maker. Close the lid and cook for 2–4 minutes, or until golden brown.
Carefully remove the waffle and place it on a cooling rack. Repeat until all batter is used.
Serve warm and topped with your favorite waffle toppings.