Whisk together water and cornstarch.
In a sauce pan, combine pineapple juice, ketchup, soy sauce, rice vinegar.
Bring to a boil. Add in the water and cornstarch mixture and cook till thickened.
Set aside sweet and sour sauce.
Prepare the vegetables. Heat a little oil in a pan.
Sauté the onion until translucent.
Add the sayote, garbanzos, eggplant, pineapple, cashews and mushrooms and cook for 3 minutes.
Add the green onions last.
Add the sweet and sour sauce and coat all the vegetables in it. Cook until vegetables are tender, but not wilted.