Make the dipping sauce and pour into small bowls or serving dish. Keep chilled until serving.
Wash and prepare your vegetables and arrange on a large plate
Combine the wholewheat flour, cornstarch and baking powder in a large bowl and whisk until well combined.
Add the sparkling water to the flour gently. Stir until just mixed. Set aside.
Dip vegetables into the batter, one at a time. Shake or brush off any excess batter. You want a light coating. Place dipped vegetables on a plate. Dip the vegetables in several batches.
Pour the oil into a deep dutch oven, deep skillet or large wok. Heat until water sprinkled on it sizzles.
Add the veggies one at a time, immediately stirring them with a woden stapula or chopstick so they don't stick to the pot. Add three of four more veggies following the same procedure.
Fry, stirring gently for 1-2 minutes. Flip and cook for 1-2 minutes more or until batter is crisp and golden.
Once fried, remove vegetables from oil and let drain on paper towels or a clean cloth. Pat gently to remove excess oil.
Repeat steps until all the vegetables are cooked.
Arrange tempura on a large serving platter and serve immediately with dipping sauce.