Combine the water, honey, and yeast in the bowl of a stand mixer. Let sit for 5 minutes, until bubbly on top.Add the cider, butter, flour, and salt. Mix on medium speed until the dough is smooth and begins to pull away from the sides of the bowl, about 3 to 4 minutes. If the dough is too wet, add additional flour, 1 tablespoon at a time. Cover the bowl and place in a warm spot until the dough doubles in size, about 1-2 hours.Preheat the oven to 425° F. Line 2 baking sheets with parchment. Bring a large pot of water to a boil. Remove the dough from the bowl and place on a floured surface. Divide the dough into 8 equal balls. Roll each ball into a long rope. To shape into pretzels, take the right side and cross over to the left. Cross right to left again and flip up. Add the baking soda to the boiling water. Boil the pretzels, 1-2 at a time, for 30 seconds. Remove with a large slotted spoon. Place the pretzel on a parchment lined baking sheet. Brush the pretzels with the egg and sprinkle liberally with salt. Bake for 10 to 15 minutes or until pretzels are golden brown.Meanwhile, make the honey mustard. Combine all ingredients in a bowl and whisk until smooth and creamy. Serve the pretzels warm, with lots of honey mustard for dipping.