Add water and sugar to a small saucepan and stir occasionally over medium heat until a gentle simmer is reached and sugar has dissolved.
Remove saucepan from heat, then add hibiscus flowers and orange peel. Cover and steep 15-20 minutes.
Pour syrup through a fine-mesh strainer into a heat-safe container. Allow it to cool before transferring to a flip-top bottle or mason jar.
Notes
Don't allow the hibiscus leaves or orange peel to boil, as this can extract more tannic/bitter notes.
Feel free to adjust the steeping time to taste. A shorter steep produces a lighter, more delicate flavor, while a longer steep makes it increasingly tart and concentrated. Start tasting around the 10-15 minute mark if you're unsure.
Use a vegetable peeler for the orange. This makes it easy to remove wide strips of peel while leaving most of the bitter white pith behind.
Let the syrup cool before judging the flavor. Aromas and flavors can seem different while the syrup is hot.
Remember that the flavor changes once diluted. The syrup should taste fairly intense by itself. Once you add a tablespoon or two to sparkling water, tea, or a cocktail, the tartness and sweetness should become more subtle.
Start small if you choose to add warming spices. Hibiscus has a beautiful flavor of its own, and strong spices can quickly overpower it.
Stored in a clean, airtight container in the fridge, hibiscus simple syrup is best used within 2-3 weeks.
For longer storage, pour syrup into an ice cube tray and freeze, then thaw individual portions as needed.