Place the vinegar, sugar, jalapeno, salt and lime juice in a small sauce pot. Bring to a simmer stir until sugar dissolves, remove from heat and let cool to room temperature.
Place the pineapple and cilantro into a large jar.
Pour the vinegar mixture over the pineapple, it should just cover the top slice.
Seal and refrigerate at least 1 day before eating.
Store in the refrigerator for up to 2 weeks. Pineapple will become more tangy with time.