Start by draining the canned pineapple and reserving its juice for the dressing. Slice the bananas, halve the grapes, segment the oranges, and chop the apples into bite-sized pieces. Toss the banana and apple slices with lemon juice to prevent browning. Combine all the fruits in a large mixing bowl and gently stir.

In a medium saucepan, mix the sugar and cornstarch together until well combined. Add the reserved pineapple juice, orange juice, and lemon juice into the mixture. Stir over medium heat until it simmers, about 2 minutes, until the dressing thickens slightly. Remove from heat and let it cool.

Once the dressing has cooled slightly, pour it over the fruit mixture in the bowl and gently fold the fruits and dressing together without mashing the fruits.

Cover the bowl with plastic wrap or a lid and refrigerate for at least 1 hour to allow flavors to meld.

Before serving, take the salad out of the refrigerator and give it a light toss. Let it sit at room temperature for about 10 minutes before serving.