Bring 3/4 cup water and the sugar to a simmer in a medium saucepan over medium heat. Stir in lemon zest and juice. Add apples; return to a simmer, and cook, uncovered, about 5 minutes. Add tapioca, and cook, stirring, until fully combined and slightly thickened, about 4 minutes. Let cool completely.
Transfer apple mixture to a food processor. Add 3 bananas, and process until smooth. Stir in yogurt. Divide among 6 bowls. Chill, if desired. Cut remaining banana into 1/4-inch pieces, and divide among puddings. Sprinkle each pudding with 2 teaspoons almonds.