Combine water, Sriracha, and yeast in a large bowl; let stand 5 minutes. Lightly spoon flour into dry measuring cups; level with a knife. Add 2 3/4 cups flour, salt, and egg to yeast mixture; stir until a soft dough forms. Turn dough out onto a floured surface. Knead until smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent dough from sticking to hands (dough will feel sticky).
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in size. (Gently press two fingers into dough. If indentation remains, dough has risen enough.) Punch dough down; cover and let rest 5 minutes. Roll dough into a 14 x 7-inch rectangle on a lightly floured surface. Roll up the rectangle tightly, starting with a short edge, pressing firmly to eliminate air pockets; pinch seam and ends to seal. Place roll, seam side down, in an 8 1/2 x 4 1/2-inch loaf pan coated with cooking spray. Lightly coat surface of dough with cooking spray; cover and let rise in a warm place 30 minutes or until doubled in size.
Preheat oven to 375°.
Bake at 375° for 40 minutes or until lightly browned on bottom and loaf sounds hollow when tapped. Remove from pan, and brush with melted butter. Cool on a wire rack.