Cut tofu into 1 1/2 x 1/2 x 1/2-in. (4 x 1 x 1-cm) “fingers”. Pat dry with paper towel then place in large bowl. Sprinkle with cornstarch and toss well to coat. Set aside.
In small bowl, whisk together vinegar, sesame oil, soy sauce and Sriracha sauce. Pour over tofu; toss to coat.
Heat oil in large non-stick skillet over medium-high heat. Place tofu in a single layer in the skillet, cooking in batches. Fry tofu about 1 to 2 min. per side, or until golden brown on all sides. Transfer batches to clean plate. Once all tofu is cooked, place back into skillet. Pour in sweet chili sauce; stir to coat. Cook about 1 min., or until heated through. Serve warm.
For extra crispy results, press the tofu to remove excess moisture. Place tofu fingers between sheets of paper towel; set on a plate. Lay a second plate on top. Then place a heavy can on the top plate. Place in the fridge overnight to allow liquid to be squeezed from the tofu.