Sriracha aioli: Combine both ingredients in a small bowl and set aside.
Carrot and daikon pickles: Combine carrots, radish, sugar, and salt in a large bowl. Using fingertips, massage salt and sugar into vegetables until dissolved. Add water and rice vinegar. Set aside.
Burgers: Combine the pork, garlic, scallions, fish sauce, chili sauce, sugar, pepper, and salt in a large bowl. Mix gently until spices are evenly distributed, but don’t overwork meat. Form into four balls.
Heat a pan with a tablespoon of oil over medium-high heat. Place burgers on pan and use a wide, stiff spatula to gently smash the balls into flat patties, about 3⁄4-inch (2-cm) thick.
Cook until the bottom of each burger has formed a brown crust, about 3–4 minutes. Flip each patty and cook through, approximately 3–4 minutes.
Assembly: Spread about 1 tablespoon sriracha aioli on the bottom of each baguette quarter. Place a burger on each baguette, topping with carrot and daikon pickles, sliced cucumber, jalapeños, and cilantro leaves.