In a large Dutch oven or heavy pot, heat oil over medium-high and cook bacon, stirring, until browned and crisp, 6 minutes. With a slotted spoon, transfer bacon to a plate. Add onion and cabbage to pot and cook, stirring, until cabbage is wilted, 10 minutes. Add vinegar, sugar, and soy sauce and cook until cabbage is crisp-tender, 10 minutes. Stir in bacon and serve.