Blend your chosen fruit, such as watermelon or mango, with sodium alginate until smooth. Strain the mixture to remove any solids, ensuring a silky consistency. Cover and let it rest in the refrigerator for at least 4 hours or overnight.

In a separate bowl, whisk together calcium lactate with cold water until fully dissolved. Stir until there are no lumps, achieving a smooth, clear solution.

Using a dropper or squeeze bottle, gently drop the fruit-sodium mixture into the calcium lactate solution. Allow each droplet to sit in the calcium bath for about 1 minute to solidify.

After one minute, carefully remove the boba using a strainer. Rinse them in fresh water to eliminate any excess calcium lactate.

For the coffee variation, mix instant coffee with hot water until dissolved. Then blend with sodium alginate, let it rest briefly, and proceed to spherification.

After rinsing all the popping boba, store them in an airtight container with a little water in the fridge for up to three days.