Heat 1 teaspoon oil in a large skillet over high heat. Add 1 1/2 teaspoons garlic and shrimp; stir-fry 3 minutes or until shrimp are cooked through. Remove shrimp from pan; keep warm.
Add remaining 1 teaspoon oil to pan. Add remaining 1 1/2 teaspoons garlic and mushrooms; stir-fry 1 minute or until mushrooms are tender. Add carrot and onions; stir-fry 2 minutes. Stir in cabbage; cook 2 minutes or until wilted.
Combine soy sauce, 1 tablespoon water, cornstarch, and Sriracha in a small bowl, stirring with a whisk. Stir soy sauce mixture into cabbage mixture. Remove from heat; stir in shrimp, tossing to coat. Serve with hoisin and tortillas.