Sautee bacon in oil until crispy. Add mushrooms and cook until they start to brown and soften. Add chopped onions and cook until they start to soften. Remove to a bowl, leaving all the oil behind.
Turn heat to high until shimmering, then add cold rice. Cook, moving constantly, until kernels start to turn golden and crispy around the edges. Add remaining vegetables and cook until al dente.
Sprinkle with rice vinegar to serve.