Divide the lime juice equally among three glasses. Add a teaspoon of sugar to each glass and two mint leaves. Place pineapple in one glass, strawberries in another, and blueberries in the third. Use the back of a wooden spoon to gently muddle the fruit and mint.
Fill each glass about two-thirds full with ice cubes. Pour 2 ounces of rum into each glass and top them off with seltzer.
Garnish your creations with fruit, mint leaves, and lime slices. Enjoy your personalized mojito creations!