Heat oil in wok or 12-inch nonstick skillet over medium-high heat until hot. Add onion; cook and stir 3 to 4 minutes or until onion is tender and lightly browned.
Add frozen green beans; cook and stir 3 minutes. Add water; cover and cook 5 to 6 minutes or until beans are tender, stirring occasionally. Meanwhile, in 1-cup glass measuring cup, mix sweet-and-sour sauce and vinegar.
Add sauce mixture, great northern beans and bacon to wok; cook and stir 1 to 2 minutes or until thoroughly heated.