Preheat oven to 200°F; preheat waffle iron. Stir together flour, sugar, baking soda and salt in a large bowl. In a medium bowl, whisk milk, vegetable oil, egg, vanilla and instant coffee. Add milk mixture to dry ingredients; whisk until just combined.
Mist waffle iron lightly with cooking spray. Pour as much batter as manufacturer suggests, usually about 1/2 cup, onto waffle iron, close and cook until golden, about 2 minutes. Place finished waffles directly on rack in oven to keep warm.
Allow waffle iron a minute to heat up, then repeat with remaining batter. Mist iron with cooking spray as needed between batches. Serve with ice cream and caramel sauce, if desired.