1. First, we need to collect watermelons and soda water. You can buy it in the store or get it through the task.

2. Then find the synthesized NPC in the game. The position of synthetic NPC in different games may be different, so it needs to be searched carefully.

3. Then, in the place where NPC is synthesized, choose the synthetic formula of watermelon special drink.

4. Then put the required materials into the synthesis position according to the synthesis formula.

5. Finally, click the synthesis button and wait for the synthesis process to be completed. After success, you can get watermelon special drink.