1. Heat oil in a pan, add garlic and sauté. Add pineapple and mix. Add salt and sugar and mix. Add one cup of water and let it cook till pineapple is soft.
2. Add two teaspoons crushed red chillies and mix. Add prawns and both the capsicums and mix. Add garam masala powder and lemon juice and mix.
3. Cook till prawns are done.
4. Serve immediately.