In a large mixing bowl, combine the diced pineapple, strawberries, mango, kiwi, and halved grapes. Gently toss the fruits together to mix evenly.
In a separate small bowl, whisk together the sweetened condensed milk, vanilla extract, and lime juice until smooth.
Pour the sweetened condensed milk mixture over the fruit and gently fold until all the fruit is coated.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to allow the flavors to meld.
Before serving, give the salad a gentle stir and garnish with mint leaves if desired.