You actually refill the 3 ml pods the same way as the 2 ml ones. There’s a little silicone plug on the side of the pod (sometimes it blends in with the plastic so it’s easy to miss). If you lift that flap with your fingernail or a small tool, you’ll see the fill port. Tilt the pod slightly while filling to avoid air bubbles and don’t overfill or it may leak a bit.
If it feels hard to open at first, try gently pressing on the edge of the plug instead of the center. After a couple of times it becomes second nature.
-
Oh, I just noticed while finishing this reply that the post is quite old, but maybe it still helps someone who runs into the same issue later.