Cut the jalapeño peppers into ⅛" round slices.
In a large sauce pan, add the sugar, vinegar, garlic powder, turmeric, and chili powder, and bring to a rolling boil over high heat. Once boiling, reduce the heat and simmer until the mixture has a thick syrup consistency, approx. 5 minutes.
Add the jalapeno slices to the sauce pan and toss to coat. Raise the heat to return to a hard boil. Once a rolling boil is achieved, immediately reduce the heat again and simmer for 4-5 minutes. Do not start the timer until a roiling boil is achieved.
Using a slotted spoon, fill the canning jars ¼ of the way full with the peppers. Add a thin layer of diced pineapples. Repeat until the jar is filled, leaving about ¼" at the top.
Bring the syrup to a boil one last time to thicken (approx. 5 minutes).
Ladle the syrup over the jalapeños until the syrup reaches about ¼" from the top.
Store in an airtight container in the refrigerator for up to 3 months. Let the jalapeños marinate for a minimum of one week, before enjoying. (*Note 3)
