In a dish, stir sugar and warm water together until mostly dissolved. Sprinkle yeast over top and let sit 10 minutes until yeast starts to activate.
In a separate bowl, combine remaining dry ingredients and whisk together well. Set aside.
Using a mixer, beat egg whites on high for 1 minute. Add oil and vinegar, beat to blend.
Add 1/3 of the dry ingredients and the yeast to the egg mixture, and beat on low for about 10 seconds. Add a 1/3 of the water, mix, then continue alternating the remaining dry ingredients with water until all are incorporated. Beat an additional minute on low, batter will be thick.
Pour batter into a greased loaf pan, smoothing top with wet spatula. Cover loosely with plastic wrap (sprayed with cooking spray), and set in a warm spot* to rise for 45 minutes.
Remove plastic wrap and bake bread in a preheated oven at 375° for 60 minutes. If bread is browning too quickly, loosely tent with foil. Bake bread until an instant read digital thermometer reads 208° F (97.8° C). This is the only way to be sure the bread is fully cooked throughout.
Remove bread from pan and place on a wire rack to cool. Slice bread only when completely cool.