Whisk soy sauce, water, brown sugar, and rice vinegar in a bowl until the sugar dissolves.
Stir in garlic, ginger, and cornstarch until smooth, then mix in the sesame oil.
Heat the vegetable oil in a large skillet over medium-high heat until shimmering.
Add the ground beef and cook, breaking it up, until browned, 5–6 minutes. Drain excess fat if needed.
Pour in the teriyaki mixture and simmer, stirring, until thick and glossy, 2–3 minutes.
Stir in green onions and red pepper flakes. Cook 1 minute, then remove from heat and garnish with sesame seeds.
Serve the beef over warm rice.
Notes
Variation: Add steamed broccoli or snap peas during the last 2 minutes. Swap ground turkey for a lighter take, or use tamari to make it gluten-free. Storage: Refrigerate up to 4 days; reheat with a splash of water to loosen the sauce.This recipe is an original creation inspired by classic Easy Teriyaki Ground Beef Recipe flavors. All ingredient ratios and instructions are independently developed.