Muddle the blackberry, mint and lime juice in the bottom of a cocktail shaker.
Add the tequila and pineapple juice, along with a few pieces of ice, and secure the lid onto the shaker. Shake for 30 seconds until the liquid is chilled.
Pour the cocktail, muddled bits and all, into 2 ice-filled cocktail glasses and top with a spritz of club soda. Serve immediately.
Notes
I recommend picking up a cocktail shaker and a few other supplies. You can enjoy happy hour at any hour for a fraction of the cost.