Make the muffin as usual (I made the cinnamon version), but cook it in a bowl instead of a coffee cup. After you take it out of the microwave, pour 1/2 C. coconut milk (or almond milk) over the top of it. Let it sit a minute or two so it can seep down throughout the entire muffin. In the second picture you can see how the milk has seeped through to the bottom of the bowl. The muffin does not become mushy; it maintains it's shape and texture, it's just milky goodness moist. :) I took a scoop out of it so you could see what I mean.
I was very surprised at how much the muffin was able to expand in the bowl; it almost completely filled the bowl! It was twice the size of the coffee cup version, and so much fluffier because of that. Whether I make a bread pudding out of it, or not, I'm making my muffin in a bowl from now on. If yours doesn't seem to get as fluffy try using 1/8 tsp. of baking soda, 1/4 tsp. cream of tartar, and 1/2 tsp. lemon juice instead of the baking powder. I haven't been using baking powder because it has cornstarch in it; maybe the baking soda and lemon juice creates more rising power. It's worth a try.
Also, I wanted to let you know that I'm continuing to add ideas for variations of the coconut muffin in the comment section of that post. So, check there periodically to see what new ideas are there, and to add your own ongoing ideas for this wonderfully versatile muffin.