Preheat the oven to 350°F (175°C). Line a cupcake tin with paper liners. In a large mixing bowl, combine flour and sugar. Add softened butter and beat with an electric mixer until the mixture resembles coarse crumbs.
Add eggs one at a time, mixing well after each addition. Pour in milk and vanilla extract; continue mixing until the batter is smooth and homogeneous.
Stir in the diced strawberries and mango gently until evenly distributed. Spoon the batter into the prepared cupcake liners, filling each about 2/3 full.
Bake in the preheated oven for 20-25 minutes or until a toothpick inserted into the center comes out clean. Once baked, remove from oven and allow to cool on a wire rack for at least 15 minutes.
While cupcakes cool, prepare the margarita glaze by combining sugar, lime juice, and triple sec in a small saucepan over medium heat. Stir until the sugar dissolves completely and the mixture slightly thickens, about 5 minutes. Remove from heat.
Using a fork or pastry brush, generously drizzle the warm glaze over each cupcake. Let the glaze set for about 10 minutes before serving, resulting in a glossy, tangy coating that complements the fruity cake.
