In a skillet over medium heat, heat oil.
Add onions and garlic and cook, stirring occasionally, until softened.
Add pork and cook, stirring occasionally, until lightly browned.
Add vinegar and bring to a boil, uncovered and without stirring, for about 3 to 5 minutes.
Add soy sauce and water. Cover, lower heat and continue to cook until pork is cooked through and sauce is reduced.
Remove the lid and increase the heat to medium. Add long beans and cook, stirring occasionally, for about 3 to 5 minutes or until tender-crisp.
Transfer to a serving platter and garnish with fried garlic bits, if desired. Serve hot.