Combine the lemon juice, sugar, orange liqueur, Triple Sec, cognac, and orange juice in a non-reactive bowl and stir until the sugar is completely dissolved. Add the Champagne and stir to combine. Cover and refrigerate until chilled, about 1 hour.
Pour into a decorative bowl or pitcher. Garnish with orange or lemon slices and fresh strawberries, if desired. Serve in Champagne flutes, wine glasses, or punch cups.