In a large stainless steel saucepan, combine the sugar, apple cider vinegar, reserved pineapple juice, turmeric, celery seed, garlic powder, and cayenne pepper.
Bring the mixture to a boil over medium-high heat, then reduce heat and simmer for 5 minutes until the sugar is fully dissolved.
Add the sliced jalapeños and drained pineapple tidbits to the boiling syrup.
Return to a boil, then lower heat and simmer for exactly 4 minutes to soften the peppers.
Using a slotted spoon, transfer the jalapeños and pineapple pieces into sterile glass jars, leaving approximately 1 inch of headspace.
Increase the heat under the remaining syrup and boil vigorously for 6 to 8 minutes until it reaches a thick, syrupy consistency.
Pour the reduced hot syrup over the peppers and pineapple in the jars, leaving 1/4 inch headspace.
Remove air bubbles, wipe the rims of the jars, and apply lids. Allow to cool to room temperature before refrigerating for at least 24 hours before consumption.