Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan and line it with parchment paper for easier removal.
In a large mixing bowl, whisk together the gluten free all-purpose flour blend, tapioca starch, potato starch, sugar, instant yeast, salt, and xanthan gum (if your flour blend does not already contain it).
In a separate bowl, combine the warm water, warm milk, eggs, vegetable oil, and apple cider vinegar. Whisk until well combined.
Pour the wet ingredients into the dry ingredients. Using a stand mixer fitted with a paddle attachment or a hand mixer, mix on medium speed for 3 to 5 minutes until the dough is smooth and slightly sticky.
Transfer the dough to the prepared loaf pan and smooth the top with a wet spatula or wet hands.
Cover the loaf pan loosely with plastic wrap or a clean kitchen towel. Let the dough rise in a warm, draft-free place for 45 to 60 minutes, or until the dough has risen to about 1 inch above the rim of the pan.
Remove the cover and bake the bread in the preheated oven for 40 to 45 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Remove the bread from the oven and let it cool in the pan for 10 minutes. Then transfer the bread to a wire rack to cool completely before slicing.
Slice and enjoy your gluten free sandwich bread fresh, or store as directed below.