Whisk brown sugar, water, fish sauce, rice wine vinegar, garlic, soy sauce, and ginger together in a bowl until brown sugar completely dissolved, about 1 minute; set aside.

Heat oil in a skillet over high heat; add chicken.

Pour 1/3 cup brown sugar mixture over chicken; cook and stir until mixture has a syrup-like consistency, 6 to 7 minutes.

Pour in remaining brown sugar mixture; cook until chicken tender and no longer pink inside, about 5 minutes.

Stir in in peanuts, green onions, and jalapeños; cook until warmed through, 2 to 3 minutes.

Garnish with cilantro and serve.