Whisk the water, Sriracha, soy sauce, and brown sugar in a bowl until the sugar dissolves. Set aside.
Heat vegetable oil in a large skillet over high heat. Add shrimp in a single layer and sear for 2 minutes without touching.
Flip the shrimp, push them to the sides of the pan, and add sesame oil, garlic, ginger, and chilli flakes to the center. Cook for 30 seconds until fragrant.
Pour the sauce into the pan. Toss everything together and let it bubble for 1-2 minutes until the sauce reduces to a thick, sticky glaze.
Remove from heat immediately. Garnish with spring onions and sesame seeds. Serve hot.
Keyword asian chilli garlic prawns, chilli garlic prawns, shrimp stir-fry