Season with salt and pepper. Heat a third of the oil in a large nonstick skillet over high heat until very hot. Add half the pork and cook until browned, about 2 minutes per side. Remove to a large bowl; repeat with the remaining pork.
Add another third of the oil to the skillet over medium heat. Add the green beans, salt, and 1/3 cup water; cook, stirring until the water evaporates and the green beans start browning about 6 minutes. Add to the pork.
Add the remaining oil, the garlic, jalapeno, and ginger to the skillet and cook, stirring, until golden, 1 minute. Add the sugar, fish sauce, and 1/4 cup water; cook until the sauce is thick and bubbling, 1 to 2 minutes. Add the pork and green beans to the sauce and toss until glazed, about 1 minute; season with salt. Serve the stir-fry with rice; top with cilantro to serve.