I will try to describe how I made it, since I told my friend Anh that I would give her a link for how to make a reversible hoodie. Except I kind of used several sources and combined them all. So hopefully this explaination will help.
I followed the idea from this website, where they made a reversible hoodie jacket. I did not buy their pattern. I have never bought a commercial pattern, as I don't think it is necessary if you already have clothes that fit you.
I used a hoodie that already fits well on me as a pattern. I lay my hoodie down flat on the fabric that I want to use, look at the seams in the hoodie, and how many pieces it took to make, and I lay flat and cut out the pieces with extra length all around for seam allowance.
My Hoodie required one back piece, two side front (left and right), two arms, and one hood. The arm pieces and hood piece I cut on a fold to make sure it was symmetrical. I probably should have cut on a fold for my back piece and cut the two front side pieces together on a fold to make sure they were symmetrical as well, but it was harder to do that with my premade hoodie pattern. So I just cut around my commercial hoodie, just be sure to give yourself enough seam allowance, otherwise it will end up smaller than you wanted. I also cut out two pocket pieces for each reversible side, using my commercial hoodie as a pattern.
To make the hoodie reversible, you have to cut out two of every pattern piece in your two different fabrics, except the waistband and cuffs. I cut one set out of the striped purple, and one set out of the solid purple.
I then cut out one waistband and two cuffs (one for each sleeve), since both sides will be sharing the waistband and cuffs.
For the construction, I used a zig zag stitch for everything except the zipper, to allow a little bit of stretch in the seams.
I added the kangaroo pockets to the front sides, according to the above website.
This website has really good information on kangaroo pockets as well. She has a great series on all types of pockets, that I highly recommend!
I then sewed the side seams, sleeves, arm holes, and hood on. Do this for both reversible sides (striped purple and solid purple), so you end up with 2 separate hoodies.
Then I sewed the hoodies to different ends of the waistband, making sure that when they are put together, both right sides will face outwards. The website has a good picture.
I then attached the cuffs to the outside side only (striped purple). Do not attach to the inside side (solid purple) yet, since you will need the sleeves open to turn the whole jacket inside out later.
I think around this point, I sewed the hood outside and lining right sides together, so the hood had its lining. At this point, you have two jackets connected by the waistband and the hood.
This is when I inserted the separating zipper. The above website did not have much info on sewing the zipper, so I did some more research.
First of all, make sure you buy a separating zipper that is long enough for your hoodie. Make sure that the zipper is reversible, meaning it has a pull tag on both sides, so it can be used on both sides.
I bought this 24 inch reversible separating zipper from Amazon, and it was the perfect size. It has nice metal teeth, so it looks durable.
This is a good tutorial on how to install a basic zipper. However, this does not work for my reversible pattern. But I would read this first because it has good information about how to install a zipper using the zipper foot, proper placement of the zipper, and gives good tips on how to move the bulky zipper pull out of the way.
This is the method that I used for installing the zipper on the reversible hoodie. There is a very good image that they have where they show the zipper sandwiched between the two sides of the fabric, with right side and wrong side clearly marked. I followed this to get my zipper inbetween the two sides. I just pinned the zipper in place instead of basting.