Heat oil for deep frying in a skillet or wok or kadai.
Once the oil is medium hot, dip the marinated chicken pieces in the batter and drop them in oil side by side to not crowd the pan.
Fry the chicken pieces on medium heat for 1 minute without turning them.
After that keep turning & frying the pieces for another 4-5 mins till golden in colour. Take it out & repeat the same with the next batch.
Now take a wok or kadai and add 1/2 tbsp oil.
Keep it on high heat and add the cubed peppers. Stir fry on high heat for 1 minute and then add the sweet & sour sauce. Mix and continue to fry on high heat for another minute till the sauce is cooked and thick.
Now add the fried chicken pieces, give a mix and continue to stir fry to coat the chicken pieces well with the sauce. This should take around 2 mins.
Serve with noodles or fried rice.