In a small saucepan over medium-high heat, prepare sushi rice according to the package directions. Let it cool for 10 minutes, then transfer it to a bowl. Add cream cheese, powdered sugar, salt, and chopped fruit and stir until well blended.
Lightly spray a 16-well ice cube tray with cooking spray. Drop a heaping 1/4 teaspoon of finely chopped strawberries into each well, spreading them evenly to cover the bottom. Fill each well with 1 tablespoon of the rice mixture, pressing firmly to pack the ingredients. If needed, add more of the rice mixture and pack until full.
To unmold the sushi, invert the tray and tap it firmly atop a cutting board. Cover and keep refrigerated (keep them cool in a lunch with an ice pack or reusable ice cubes).