The following post is a repeat from my old dead blog.
Take two shirts of similar size. Make sure one of them has long sleeves (the long-sleeved shirt will be the outside part of the bag, and the other shirt will be the lining, so make sure you like to look at the long-sleeved shirt).
Cut off the tops of the two shirts.
I would highly recommend not using a stretchy sweater for the long-sleeved shirt. Sewing two stretchy shirts together totally sucks.
Turn the short-sleeved shirt inside out. Cut off the sleeves and sew the open sides shut so that it looks like a rectangular tube.
With the long-sleeved shirt right-side-out, and the rectangular tube inside-out, place the tube over the long-sleeved shirt.
Pin the top openings together and sew.
Unfold the two shirts from each other so that everything is right-side-out.
Sew along the bottom hem of each shirt (seperately!) to seal them off.
Tuck the inside shirt into the outside shirt’s opening.
Now you have two choices: you can simply tie the sleeves together and call it a day like a lazy jerk (not pictured: being a lazy jerk), or you can add a clever detail to the sleeves that will attach them together and look cute.
Take some flat bracelets that you never wear, and pin the edge of each sleeve around those bracelets.
And then sew it.
And there’s your tote bag.