Milk, buttermilk, yogurt: When used in place of water, these ingredients soften the crumb and crust, and, especially in the case of buttermilk and yogurt, add flavor to the bread. They will also accentuate the browning of the crust.
Flavored Water: When making onion or garlic flavored breads, one thing that can be done is to flavor the water used to make the dough. Typically dry onions are added to boiling water to rehydrate the onions then allowed to cool. A small amount is all that is needed, say, 1/4 Cup of onions in 2 cups of hot water. You may add the re hydrated onions to the mix or use it as topping, or not. The water will add a wonderful aroma and flavor to the bread. Dry garlic chips may also be used in this manner. Onion rye, onion bagels benefit from this treatment.
Fats (oils and butter): Fats soften crumb and crust, add flavor and lengthen life of bread. The amount varies widely. Sandwich breads usually have somewhere between 2% to 10% of the flour weight, whereas a brioche could have 80%, even 100% (!!) the flour weight in butter.
Sugar (honey, molasses, sugar, syrup): Sweeteners also add flavor, and, in some cases like honey, can also delay staling. It is a myth that the yeast needs additional sugar in order to work in the dough. In fact, in high quantities, sugar can negatively affect the yeast. Typically sweeteners are 5% to 15% of the flour weight.
Seeds and nuts (sesame, flax, pecans, sunflower, etc.): These are really yummy, and are often toasted before adding them to the dough, usually at the end of the dough’s development. Sometimes, the addition of seeds and nuts requires the addition of more salt, bumping the salt percentage up to 2.5% or so.
Dried fruits: These are excellent additions to breads, especially raisins and dried apples. It’s a good idea to soak these for a half-hour or even overnight before adding so that those that end up on the surface don’t burn. Dried fruits are typically at 15% to 30%.
Spices and herbs: These can add a lot of flavor to breads, but be careful not to overdo it. Dried herbs are best. Traditional additions include dill, rosemary and cinnamon. Typically these are about 2% to 3%.
Note: Tree-bark spices like cinnamon and allspice contain anti-fungal compounds that retard the activity of the yeast. You may want to bump the yeast up by about 50% if you’re using these kinds of spices in the dough.