In a small bowl, combine the warm milk and warm water. Stir in the sugar and sprinkle the yeast over the liquid. Let it sit for about 5-10 minutes, or until it becomes frothy.
In a large mixing bowl, combine the flour and salt. Make a well in the center and pour in the yeast mixture and olive oil.
Mix the ingredients until a dough forms. Knead the dough on a floured surface for about 5-7 minutes, or until it becomes smooth and elastic.
Place the dough in a lightly oiled bowl, cover it with a clean kitchen towel, and let it rise in a warm place for about 1-2 hours, or until it has doubled in size.
Preheat the oven to 375°F (190°C).
Punch down the risen dough and roll it out into a large circle on a floured surface. Transfer the dough to a baking sheet lined with parchment paper.
Arrange the candied fruits and pine nuts on top of the dough. Optionally, sprinkle some lemon zest over the toppings.
Bake in the preheated oven for about 20-25 minutes, or until the edges are golden brown.
Remove from the oven and let it cool for a few minutes. While it's still warm, sprinkle sugar over the top.
Slice and serve the Coca de Sant Joan at room temperature.