Make the bilo-bilo dough: Place the glutinous rice flour in a medium bowl. Add the warm water gradually, mixing until a soft, smooth dough forms. It should feel pliable and not sticky. Add a few drops of water if crumbly, or a little more flour if sticky.
Roll the dough into small balls about 3/4 inch wide (roughly the size of a marble). Keep the finished balls on a plate while you prepare the coconut dessert base.
Bring the 2 cups water to a boil in a medium-heavy pot over medium-high heat. Add the sweet potato and cook until it is beginning to soften, about 6 to 8 minutes.
Add the tapioca pearls. Reduce the heat to maintain a steady simmer and cook, stirring often so the pearls do not settle on the bottom. Cook according to the package directions, until the pearls are mostly translucent.
Add the rice balls to the pot and stir gently. Simmer until the balls float and are cooked through, about 4 to 5 minutes.
Turn the heat to low. Stir in the coconut milk, brown sugar, and salt. Warm gently without allowing the mixture to boil hard, stirring until the sugar dissolves.
Add the sliced banana and optional jackfruit. Cook gently just until the banana is heated and tender, about 2 minutes. Taste and add a little more brown sugar if desired.
Serve warm in small bowls. The dessert will thicken as it stands; loosen leftovers with a small splash of water or coconut milk when reheating.