In a mason jar or shaker, add pineapple, jalapeño, and lime juice. Muddle together until smashed and combined. Add vodka, pineapple juice, and a few ice cubes. Cover and shake.
In an old-fashioned glass, add ice, and pour cocktail in glass and garnish with pineapple or jalapeño slices as desired.
Notes
You can skip the shaking step if you want - just add the ice to your muddled ingredients, pour in liquids, and stir.