Heat water and sugar in a small saucepan over medium or medium-high heat to bring to a boil, stirring most of the time with a whisk or wooden spoon.
Lower heat, if needed, to keep at a simmer for a few minutes, until sugar is dissolved and water is clear. Stir frequently.
If using tender herbs like mint, basil or tarragon, chop while syrup simmers. Remove from heat and stir in herbs. Cover and let stand for 20-30 minutes.
If using spices like cinnamon sticks, cardamom pods, vanilla beans, fresh ginger or citrus peel, simmer in the syrup once the sugar has dissolved, for an additional few minutes. Then remove from heat, cover and steep.
If you added any herbs or spices, strain after steeping. Store in the refrigerator up to 4 weeks.