Spray a large nonstick wok or frying pan with cooking spray and heat over a medium heat. Add the onion and garlic and stir-fry for 3 minutes, then add the peppers and stir-fry for a further 3 minutes.
Add the broccoli florets, baby corn and courgettes to the pan and continue to stir-fry for 5 minutes. Add the bamboo shoots and water chestnuts and toss to mix in.
Mix together the soy sauce, cornflour, stock, ginger juice and sweet chilli sauce in a small bowl until smooth.
Make a space in the centre of the stir-fried vegetables with a wooden spoon so that the base of the pan is visible. Pour in the sauce mixture, bring to the boil and cook, stirring constantly, until it starts to thicken. Toss the vegetables to coat thoroughly with the sauce.
Transfer to a warmed serving dish, sprinkle over the bean sprouts and serve immediately.