Here's my recipe for a very nice sweet and sour sauce.
2 tbsp sugar
3 tbsp vinegar
3 tbsp tomato puree
3 tbsp organce juice
1.5 tbsp soya sauce
1.5 tbsp cornflour blended with 4 tbsp water
Mix all the ingredients tohether and sling them into your stirfry near the end of cooking. Wait for the sauce to heaten and thicken and serve.