Peel oranges so that the white skin is completely removed. Remove the fillets with a sharp knife between the parting skins. Squeeze the skins and collect 250 ml of juice. Mix pineapple juice with orange juice and tequila. Pour the juice mixture into a punch bowl and fill up with sparkling wine. If you like, put grenadine and orange fillets into long drink glasses and fill up with the punch. Decorate with lemon balm