Cut the veg in to rough, thumb sized shapes and set aside.
For the sweet chilli sauce, place the sugar, vinegar and water in a bowl with the finely chopped garlic, ginger and red chilli. Bring to the boil and leave to simmer away gently.
Meanwhile, fill a pan with 1 liter of vegetable and place on a medium heat for around 2 minutes. Using a meat thermometer or electronic temperature probe, bring the temperature to 160C and turn down the heat.
To make the tempura, at the last minute mix together the flours, salt, baking powder and soda water with ice cubes to a paste. It shouldn't be as thick as wallpaper paste but slightly thicker than soup and should coat the back of a spoon easily. Don't over whisk at this stage - it's better to have small lumps of flour, as these will crisp up nicely
Coat the vegetables in the plain flour, before adding to the tempura batter. Fry these in small batches for 3-4 minutes, depending on size until nicely crisp and cooked through.
Drain on kitchen paper and serve alongside the sweet chilli sauce.