Reserve 1/2 cup of pineapple juice from the can of pineapple reserve 2/3 of the pineappple chunks. Set aside.
Combine the hot water salt, sugar and ketchup,stirring until the sugar is dissolved. Add the vinegar and pineapple juice. Stir well and set aside.
To marinade the chicken
Cut the chicken inti one inch chunks and place in a bowl. Add the garlic powder and onion powder, sesame oil, white pepper and salt. Mix well until all the chicken pieceds are evenly coated. Set aside for 5 minutes.
To make the batter
Mix together the flour, cornstarch, baking powder and baking soda in a medium size bowl. Add 2/3 cup of ice cold water. With a fork, mix until you have a smooth batter. Add a tablespoon of Canola oil. Mix again and set to one side.
To cook the chicken
Add enough oil to the wok to immerse a good handful of chicken chunks. Heat the wok until the oil reaches 335ºF.
Place 6 pieces of the chicken into the batter, moving it about so the chicken is well coated. With tongs place the chicken in the oil, one piece at a time so they remain separate. Fry for 2-3 minutes until the batter is a nice golden brown. Flip the pieces over during cooking so all side brown evenly.
Use a slotted spoon to remove the chicken to a paper towel lined plate. Repeat in batches until all the chicken is cooked.
to assemble the sweet and sour sauce
Add the canola oil to the wokk and bring to a medium high heat. Add the red onion and bell peppers. Stir fry for 30 seconds.
Add the sweet and sour base sauce and bring to a boill. Reduce the heat to a simmer.
Make a slurry with the cornstarch and water and stir ingradually until the sauce thickens. reduce the heat and taste test the sauce. Add more salt, sugar or vinegar to you taste.
Add the pineapple chunks and stir until warmed through.
If using tempura battered chicken pieces add the chicken, toss the mixture and serve immediately. over rice.