Honey (Best Option)
1 tablespoon honey per 1 tablespoon brown sugarHoney works well as a substitute because it contains natural sugars (fructose and glucose) that caramelize similarly to brown sugar's sucrose and molasses content. The moisture in honey helps maintain the sauce's consistency and aids in browning proteins and vegetables.
When using honey, reduce other liquids slightly to compensate for its moisture. Also, add it towards the end of cooking to prevent excessive burning due to honey's lower burning point.
The final stir-fry will have a slightly different sweetness character, with a subtle floral note, but it will retain the desired balance and glossy finish typical of brown sugar-based sauces.