Mix the sugar, ½ cup warm water and the yeast in a mixing bowl and set aside for five minutes or until the mixture starts to froth, indicating the yeast is alive and well.
Sift all the flours, salt, and baking soda into the bowl. Knead on low speed in a stand mixer or by hand for about 3 minutes, trickling in 1 cup of water until you have a dough that's smooth and supple. You might not need all of the water.
Add the oil and continue to knead until the oil has been absorbed by the dough, about 1 more minute.
Place the dough in an oiled bowl, turning over once to coat all over with oil, cover with a kitchen towel, and set aside in a warm spot for 1 ½ hours until the dough has more than doubled.
Fold the dough over itself to deflate. Form into a ball again, then divide into 8 equal sized pieces. Shape each piece into a smooth ball.
Place the buns on a baking sheet that's either been lightly greased or is lined with parchment. Space the buns at least a couple of inches apart. Flatten the tops slightly with your fingers, if you like. Cover the buns loosely with a kitchen towel and set them in a warm spot to rise for an hour.
Preheat the oven to 370 degrees.
Before the buns go into the oven, you can sprinkle seeds on the tops of the buns if you like. To do this, mix 1 tsp vegetable oil, 1 tbsp nondairy milk and ¼ tsp maple syrup in a bowl. Brush the tops with this mixture, then sprinkle sesame seeds or poppy seeds on the tops.
Place the buns in the oven and bake 25 minutes. Remove the buns to a rack and allow them to cool thoroughly before serving.