Whisk together the sugar, soy sauce, water, garlic, vinegar, Sriracha, and cornstarch in a bowl.
Heat 2 tbsp of olive oil in a large skillet over medium heat and half of the tempeh slices; cook until golden brown. Transfer the cooked pieces to a paper towel lined plate to drain off any excess oil. Repeat with remaining tempeh pieces and remaining oil.
Add the sauce mix to the now empty skillet and simmer over medium-low heat until thickened for about 5 minutes; transfer to a bowl.
Toss tempeh slices and half of the sauce in a large bowl; mix gently.
Lay out the tortillas and layer with tempeh, bok choy, cilantro, radishes, and scallions, in the center of each tortillas. Wrap the ingredients in the tortilla and serve with remaining sauce. Enjoy!