Can I leave some of the muffin cups empty when baking in a muffin pan?
"Can I leave some of the muffin cups empty when baking in a muffin pan, or should I fill the empty ones with water?"
Your muffins will come out exactly the same whether the empty cups are filled with water or not. Adding or not adding the water shouldn't effect your muffin pan, either, so go ahead and fill only half the muffin cups with batter if you like.
For more tips on making muffins, see our video, How to Make Bran Muffins.