In a large bowl, combine the noodles with enough warm water to cover. Soak until just tender, about 30 minutes, then drain and set aside.
In a small bowl, combine the fish sauce, vinegar, lime juice, tamarind paste, crushed red pepper, and sugar; stir until the tamarind paste and sugar dissolves and is well blended. Set aside.
In a wok or large skillet, heat 2 tablespoons of the oil over medium-high heat. Add the garlic, and cook, stirring, for about 30 seconds or fragrant. Add the shrimp and cook until shrimp becomes pink in color and mostly cooked through, about 2 minutes. Transfer shrimp to a plate and cover loosely to keep warm.
Add the eggs to the skillet and cook, stirring to break up into small pieces, about a minute. Add the white part of the onions and cook for 2 minutes to soften (add more oil if needed). Add the sprouts, Bonito flakes, green part of the onions, fish sauce mixture, and most of the noodles; cook over medium heat until mixed well and warmed through, stirring frequently. Note: I add most of the noodles at first, then add more based on how well the sauce is covering everything in the skillet. Sometimes the noodles soak up more sauce depending on the brand and type.
Add the reserved shrimp and peanuts, and cook for 30 seconds to incorporate into the noodles. Finally, toss with the cilantro and serve immediately with lime wedges and Sriracha sauce on the side.
Dried Bonito flakes, known as katsuo-bushi or katsuobushi in Japanese cuisine, are thin flakes of dried, smoked bonito fish. Like dried shrimp or shrimp paste (often used in Pad Thai), bonito flakes add a savory flavor to any dish.I buy Bonito flakes at our local Whole Foods, which is easier than going to an Asian market for harder to find dried shrimp or paste. Bonito is sliced so thinly it melts into soups, sauces, or stews for a umami flavor boost.