Drain the lychee from the can, saving the syrup. You can make the jelly with or without the lychee pieces. If using, cut the lychees into small pieces for easier incorporation into the jelly.

In a saucepan, combine the water and agar-agar powder and bring it to a boil over medium heat. Stir occasionally to ensure the agar-agar dissolves completely.

Once the agar-agar mixture boils, add in the lychee syrup and sugar. Stir until the sugar has dissolved and the syrup is fully combined. Then, add the chopped lychee pieces (if using) to the saucepan and mix well.

Pour the mixture into a shallow pan or container and allow it to cool down to room temperature. After that, refrigerate for 1–2 hours until it sets and becomes firm.

Once the jelly is firm, cut it into cubes or desired shapes. Add the homemade lychee jelly to your bubble tea, along with your favorite tea, boba, and ice. Stir and enjoy!