Nutrition per serving may change if servings are adjusted.
2 cups mango juice
1 cup cold water
4 envelopes unflavored gelatin
1/3 cup sugar
1 cup cold orange juice
1 cup diced strawberries
1 cup diced mango
Bring mango juice to a boil in a small saucepan over high heat.
Meanwhile, pour water into a large heatproof bowl. Sprinkle gelatin over the water; let stand for 3 minutes. Add the mango juice and stir to completely dissolve the gelatin, 2 to 3 minutes. Add sugar and stir for 1 minute to dissolve. Whisk in orange juice.
Refrigerate until the mixture is the consistency of thin pudding and is just starting to set around the edges, 1 to 1 3/4 hours. The time will vary depending on the size of your bowl and how cold your refrigerator is. After 1 hour, start checking every 5 to 10 minutes because it thickens quickly after that.
Gently but thoroughly whisk the mixture until it's uniform. Stir in diced fruit. Pour into a 9-by-13-inch pan. Cover the pan with plastic wrap, without touching the jello.
Refrigerate until very firm, about 3 hours. To test if it's ready, touch it with your finger. If your finger does not stick, it's done.
Run a small, sharp knife around the edge of the pan. Cut into 16 squares then gently pry the squares out with a butter knife.
Make Ahead Tip: Refrigerate for up to 3 days; unmold just before serving.