Prepare gulaman: Follow the package instructions. Let it set, then cut into cubes.
Make syrup: Combine brown sugar, water, and knotted pandan leaves in a small pot. Heat over medium-high, stirring until the sugar dissolves. Once boiling, lower to medium-low and cook for about 15 minutes until slightly thickened. Remove pandan and let cool.
Cook sago: Follow the package instructions, adding pearls to boiling water. Cook until translucent, then drain and rinse under cold water. Mix with 2 tablespoons of syrup to prevent sticking.
Prepare grass jelly: Drain and cut into cubes.
Assemble: Add sago, gulaman, grass jelly, ice, syrup, and cold water to glasses or a pitcher. Stir and adjust with more syrup or water to taste.
Notes
Gulaman: Use powder or a bar; follow package instructions. Gelatin works but is softer and not plant-based.
Brown sugar: Dark gives more flavor; light brown sugar or panutsa works too.
Pandan: Knot or bruise the leaves. Substitute pandan extract, vanilla, or banana essence.