Prepare the Shrimp: Season the shrimp with salt and pepper. Coat them evenly with cornstarch.
Fry the Shrimp: Heat oil in a deep skillet or wok over medium-high heat. Fry the shrimp in batches until golden and crispy, about 2 to 3 minutes per side. Drain on a paper towel-lined plate.
Make the Sauce: In a bowl, whisk together mayonnaise, sweet chili sauce, rice vinegar, sriracha, and sugar. Adjust the spice level to taste.
Toss and Serve: In a large bowl, toss the fried shrimp with the sauce until well-coated. Garnish with green onions and diced tomatoes. Serve immediately.
