Bring hibiscus flowers and 1 qt. (4 cups) water to boil in medium pot over medium-high heat. Remove from heat and let steep about 20 minutes.
Meanwhile, press sharp side of 10 cloves into one orange. Repeat with remaining cloves and orange. Quarter oranges.
Strain hibiscus mixture into large (10-12 qt.) pot; discard solids. To pot, add remaining 5 qts. (20 cups) water, clove-studded orange pieces, tejocotes, guava, sugar cane sticks, piloncillo, apple, pear, prunes, walnuts, raisins and cinnamon sticks. Bring water mixture to boil over medium-high heat, stirring occasionally to dissolve piloncillo. Reduce heat to low. Simmer, stirring gently, until flavors are completely infused and fruit is tender, about 1 hour.
To serve, ladle drink and fruit into serving mugs. Add liquor, if desired. Serve warm or chilled.