Pour your bottle of red wine into a medium saucepan set over low heat. Add the sugar, orange slices, lemon slices, cinnamon sticks, cloves, and star anise directly into the pot. Stir everything together gently so the sugar begins to dissolve into the wine.
Keep the heat on low and let the wine warm gradually, stirring every few minutes. This step is really about patience, since rushing it on high heat can boil off the alcohol and leave the flavor flat. You're looking for steam, not bubbles.
Once the wine is hot, let it sit on low heat for about 20 to 25 minutes so the spices have time to fully infuse. The longer it simmers gently, the deeper and more fragrant the flavor becomes, so don't rush this part.
If you're using brandy, stir it in during the last five minutes of cooking. Adding it too early can cause more of the alcohol to cook off, so this timing really does make a difference in the final taste.
Turn off the heat and ladle the wine through a fine mesh strainer into heatproof mugs, leaving the spices and fruit behind. Serve it immediately while it's still warm and fragrant, with a fresh orange slice or cinnamon stick as a simple garnish.