Heat coals of grill or fire pit. Or heat an oven to 500ºF.
Cut 8 (18-by-18-inch) squares of aluminum foil. Lay down 4 double layers of foil and divide gingersnaps evenly among the squares. Divide fruit evenly and place on top of gingersnaps. Dot with the butter.
Mix sugar, salt, and lime zest in a small bowl. Sprinkle the sugar mixture evenly over fruit, drizzle with the lime juice and brandy, and seal packets.
Once coals are ash covered, lay packets over them and cover with lid of grill. If cooking in a fire pit, carefully try to partially bury packets in hot coals. Cook for 10 minutes on the coals or 12 to 15 minutes in the oven. Remove from the heat and open carefully, as steam inside packet is very hot. Serve on plates as is, or spoon into shallow bowls and top with vanilla ice cream.