Add the sliced peaches and raspberries to a large pitcher.
Pour in the wine, simple syrup, and peach schnapps. Stir to combine.
Chill the fridge for at least 1 hour to overnight.
To serve: Add some fruit from the pitcher into a wine glass. Fill the glass halfway with sangria and then the rest of the way with champagne. Serve immediately.
Notes
You can use frozen fruit instead fresh if peaches and raspberries aren't in season.
To make homemade simple syrup: Add equal parts water and sugar to a saucepan. Place over medium heat and cook until sugar has dissolved. Remove from the heat and allow the syrup to cool completely.