Combine flour, sugar, instant yeast, and salt in the bowl of a stand mixer with the dough hook attachment.
Using a low speed, add the sourdough discard and water until well combined.
Increase the speed to medium (3 or 4) and knead for 5 minutes until a smooth dough forms and pulls away from the sides of the bowl. (You may need to add one tbsp of water or flour to reach the desired consistency - the dough should not be sticky or shaggy.)
Place the dough in a large greased bowl and cover with plastic wrap or plastic shower cap. Let the dough rise until doubled in size. (about 90 min)
Once the dough has doubled, roll it out on a smooth surface and divide into 8-10 equal pieces.
NOTE: It may be helpful to weigh your dough before rolling out and divide the weight by either 8 or 10 depending on the number of bagels you want. Then you can weigh the small chunks of dough and get equal bagels.
Roll each piece of dough into a ball and push your thumb through the ball to create a bagel form.
Place the bagels on a cookie sheet lined with parchment paper. Cover bagles with a towel and let them rest for about 20 minutes.
Preheat the oven to 425℉.
While the bagels are resting, bring a pot of 2 quarts of water to a boil with 2 tbsp of baking soda.
Place the bagels 1 or 2 at a time into the boiling water for 20-30 seconds on each side. Using a slotted spoon, remove the bagels and place back on the cookie sheet. Make sure the bagels float on the top of the boiling water. This ensures that they will rise in the oven. If your bagels aren't floating see notes at the end.You can also use the handle of the slotted spoon to reshape the hole of the bagel if needed. Brush the egg wash on each bagel and add your favorite toppings such as everything bagel seasoning, poppy seeds, or a cinnamon crunch mixture (see note).
Bake at 425℉ for 20-25 minutes until golden brown. Slice before serving and enjoy!