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. Or follow package directions.
Using a small bowl, combine the fish sauce, vinegar, tamarind paste, crushed red pepper, and sugar; stir until the tamarind paste and sugar dissolves and is well blended. Set aside.
Heat the oil over medium-high heat in a large skillet or wok. Add the garlic, and cook, stirring, for 30 seconds or just fragrant. Stir in the meat and cook until the just cooked through, about 2 minutes. Transfer to a plate and cover to keep warm.
In the same skillet, cook the eggs about 1 minute, stirring to break up into small pieces. Add the white part of the onions and cook for 2 minutes to soften. Stir in the sprouts, Bonito flakes, green part of the onions, fish sauce mixture, and noodles, and cook until mixed well and warmed through, stirring frequently. Taste, and sprinkle in more Bonito flakes, as desired.
Toss in the reserved meat and peanuts, and cook for 30 seconds to incorporate into the noodles. Sprinkle with the cilantro and lime juice; serve immediately with lime wedges and Sriracha sauce on the side.
Notes
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.
Bonito flakes were easier to find than dried shrimp or paste in our area. Bonito is sliced so thinly it melts into soups, sauces, or stews for a umami flavor boost.