Remove stems and cut each pear lengthwise in half, removing the core.
Cut off the ends of the lemons and slice into ¼-inch thick slices.
Add the pear and lemon slices to a large pitcher.
Add cinnamon sticks, leaving some aside for garnishing.
Pour the wine and vodka (optional) over the fruit in the pitcher and stir. Cover the pitcher with plastic wrap and refrigerate for at least 4 hours, up to 8.
When ready to serve, cut the remaining pears lengthwise into ¼-inch thick slices.
Pour the sangria mixture into a glass. about a third of the way. Top it off with seltzer. Add a pear slice, cinnamon stick, an ice cube if your heart desires, and a sprig of thyme.
