Place a wire rack on a baking sheet. Pat the shrimp dry with paper towels. Using two skewers side by side, skewer the shrimp snugly against each other, about 5 shrimp per set of skewers. Place the skewers on to the prepared rack.
Whisk together 2 tbsp olive oil and 2 tbsp Sriracha, and use a grill brush to evenly coat both sides of the skewered shrimp. Sprinkle evenly with salt and pepper. Refrigerate for half an hour.
Bring a grill or grill pan to high heat and use tongs to place the shrimp firmly onto the grill, letting cook for 3 to 4 minutes on each side or until cooked through and charred outside. Transfer the skewers to a plate and use tongs to slide the shrimp off the skewers.
Use a fork to combine the remaining 2 tbsp of Sriracha with the mayonnaise. Assemble the tacos starting with a few shrimp, followed by the red cabbage slaw and Sriracha mayo. Serve with lime.
*Red cabbage slaw: Whisk together 1/3 cup sour cream, 1 tbsp olive oil and 1 tbsp lime juice in a medium bowl. Add 2 cups thinly sliced red cabbage (from about half of a small red cabbage), 1/2 cup chopped green onion and 1/2 cup shredded carrot (from about 1 large carrot), and toss to coat evenly. Season with salt and pepper.