Step 1Combine a cup of sugar with a cup of water in a small saucepan and bring the mixture to a boil, stirring until the sugar dissolves, about 1 minute.
Step 2Remove it from the heat and cool.
Vanilla simple syrup: Add half a vanilla bean to the mixture before bringing it to a boil.
Orange: Add the peel from half an orange to the mixture before bringing it to a boil; after it cools, add 2 tablespoons Grand Marnier.
Coffee: Replace the water with strong brewed coffee.
Herbs: Add a tablespoon of chopped herbs (or a few sprigs) such as rosemary or lavender.
Liqueurs or juices: Add 2 tablespoons of flavored liqueur or 1 teaspoon of an extract, or replace part of the water with fruit juice.
Caramel: Put the sugar in a medium, heavy-bottomed pan with high sides and turn the heat on high. Melt the sugar, stirring with a wooden spoon, until it's a deep golden brown, about 7 minutes. Once golden, turn off the heat and add a cup of hot water. Watch out: It will boil up. Let the boiling subside and stir; return to low heat if any sugar solids remain. Cool.
Caramel-spice: Infuse the hot water for the caramel syrup with spices such as cinnamon or black peppercorns or even chiles. Remove or strain the spices.