In a medium saucepan, combine chicken broth, soy sauce, sriracha, and sesame oil. Bring to a simmer over medium heat.
In a separate pot, cook ramen noodles according to package instructions. Drain and set aside.
In a large skillet, heat vegetable oil over medium-high heat. Add chicken pieces, season with salt and pepper, and cook until browned and cooked through, about 5-7 minutes.
Add minced garlic and grated ginger, cooking for an additional 1-2 minutes until fragrant.
Stir in baby spinach and cooked ramen noodles, mixing well to combine.
Pour the broth mixture over the noodles and chicken, stirring to heat through.
For the creamy garlic sauce, whisk together mayonnaise, sour cream, lemon juice, garlic powder, salt, and pepper in a small bowl until smooth.
Serve the ramen in bowls, drizzling the creamy garlic sauce on top. Garnish with sliced green onions and sesame seeds, if desired.