You will need a plain, loose fitting t-shirt or long sleeve shirt, scissors, a needle, thread, and a heavy object.
To start, cut out the neck of the shirt and the sleeves so you have a muscle tank. On the back of the shirt cut a strip going down the middle of it starting up at the collar going down to almost the very bottom of the shirt. At the bottom of the strip cut to either side directly across to the seam on the side of the shirt. Take this center strip and cut it into three strips and braid it all the way down. While braiding place the heavy object at the base of the braid so you can pull on it without the shirt moving. Now sew the end of the braid together so it will not come undone.
After this is done the back of your shirt is a braid and two flaps on either side. On the flaps, cut from the bottom of the arm hole directly across so the shoulder section is removed from the flap. Do this on either side. It should be as if the section where your shoulder blades would go can be lifted up and folded over, more flaps. These flaps should still be connected to the front of the shirt through the shoulders of the shirt. Now cut the flaps on the sides into three or four strips. Cut each of those strips into three strips so you can braid them. As you braid them, sew them onto the large center braid.
As you go, remember to move the large heavy object you are using to the bas of each braid, it may not seem necessary but the braiding will go faster if you can pull on the braid a bit without the shirt flying everywhere.
If you have done everything correctly up to this point you should have one braid going up the center on the shirt with either three or four braids connected to it from each side. You should also have two flaps where the shoulder blades would go coming from the front of the shirt over the shoulders. Take both of these flaps and trim them as they may need to be so they are straight and don’t flare out or anything. Now cut both flaps into three strips and braid them all the way down. Sew both of the braids to the top of the main, center braid.
If everything was done correctly you should be left with a tank top with braids as the shoulders and as the back, and each braid should be connected to the one center braid going down the middle.