In a bowl, whisk together the egg and chilled soda water. Add the flour and corn starch and mix until well combined.
Add the shrimp to a separate bowl and sprinkle with salt and black pepper. Pour the tempura batter over the shrimp, making sure each one is coated.
Heat the oil in a large skillet over medium-high heat. Fry the shrimp for 3-4 minutes on each side until crispy. Drain excess oil on paper towels.
In a saucepan, combine the coconut milk, coconut cream, mayonnaise, sweetened condensed milk, corn starch, and salt. Whisk until well combined.
Cook the coconut sauce over medium heat, whisking constantly, until it thickens and becomes smooth.
Place the fried shrimp in a large bowl, pour the coconut sauce over them, and toss to coat.
Garnish with chopped green onions and serve hot.