In a small saucepan, combine water, sugar, and thinly sliced jalapeno.

Bring the mixture to a boil, stirring to dissolve the sugar.

Reduce heat and simmer for 3-5 minutes to infuse the jalapeno flavor.

Remove from heat and let cool completely.

Strain the syrup to remove the jalapeno slices.

In a large pitcher, combine the jalapeno syrup, pineapple juice, and dry sake.

Stir well to ensure all ingredients are combined.

Refrigerate the sangria for at least 1 hour to allow the flavors to meld.

Serve the sangria over ice in tumblers.

Garnish each glass with a slice of pineapple and a fresh mint sprig.