Mix the dough: In a large bowl, combine the warm water, granulated sugar, and active dry yeast. Let bloom for about 5 minutes, until foamy. Add the sourdough discard and mix until dissolved. Add the sea salt and bread flour and mix until a dough forms. Cover and let rest for 30 minutes.
Stretch and fold: After resting, uncover the dough. With wet hands, perform one full set of stretch and folds, turning the bowl a quarter turn between each fold. Cover and let rise for 1–2 hours, until nearly doubled.
Shape the bread bowls: Turn the dough out onto a clean surface and divide into 6 equal portions, about 200 g each. Shape each piece into a tight round by tucking the dough underneath itself and turning to create surface tension. Place on a parchment-lined baking sheet with space between each.
Proof: Lightly dust the tops with flour. Cover and let rise in a warm place until just about doubled.
Bake: Preheat the oven to 450°F. Place a shallow pan with ½–1 cup hot water on the bottom rack of the oven. Bake the bread bowls for 25 minutes, until deeply golden and crusty.
Cool and serve: Let cool completely before cutting. Slice the top off at an angle and gently remove the interior, leaving the crust intact. Fill with soup and serve.