Begin by pouring freshly squeezed lemon juice into a large mixing bowl to prevent oxidation. Core and chop the large apple into bite-sized pieces, then add it to the bowl, ensuring it's coated in lemon juice. Slice the bananas just before adding them, and gently toss them with the apple to maintain their bright color and prevent browning.

Rinse the blueberries under cold water and set them aside to drain. Hull the strawberries and cut them into quarters, then add them to the bowl along with the grapes, either whole or halved, for added texture. Mix the fruits gently to incorporate the apple and banana, creating a colorful base.

Open the cans of pineapple and mandarin oranges, draining the pineapple tidbits but reserving the juice. In the same bowl, incorporate both the tidbits and the mandarin oranges. Add about ¼ cup of the reserved pineapple juice to the fruit mixture for enhanced juiciness.

Pour the sweetened condensed milk evenly over the medley of fresh fruits. Using a large spoon or spatula, gently toss the fruits to coat them thoroughly in the creamy dressing.

Cover the bowl with plastic wrap or a lid and refrigerate for at least 30 minutes. When ready to serve, give the salad a gentle stir and transfer it to a colorful serving dish.