If we have jalapeño popper leftovers and I want them crispy I will reheat in the air fryer. I preheat it to 350 degrees then toss in my poppers for 3-5 minutes. If using this method be careful, you just want to reheat not overcook. But you can reheat small or large batches easily in the air fryer.
Reheating in the microwave start with using 40-second intervals for 5 or more poppers. I have to be in a big hurry to use the microwave method. Reheated bacon tends to be chewier when using the microwave and I enjoy a little crunch to mine.
Using your oven is also an option but that requires a lot more time waiting since preheat takes longer. If it is your only appliance set to 350 for preheat, then put the jalapeño poppers in for 3-5 minutes.