1. Place a plate in oven and preheat to 200°F. Preheat waffle iron (to medium, if it has temperature settings). In a large bowl, whisk flour, baking powder, sugar and salt. In a medium bowl, whisk milk, oil and 1/4 cup water. Pour milk mixture into flour mixture and whisk until smooth. Stir in chocolate chips.
2. Mist waffle iron with cooking spray. Pour as much batter onto waffle iron as manufacturer recommends (usually about 1/2 cup). Close iron and cook until waffle is golden and puffed, 2 to 3 minutes. Place on plate in oven.
3. Repeat with remaining batter. Between making individual waffles, wipe iron periodically with a paper towel to remove bits of chocolate and mist iron with cooking spray. Serve hot.