I saw this idea over on Craftynest and kind of did my own thing with it. All you need is a tank top that has front and back neck lines that are the same. I also did a freezer paper stencil on mine and added a crochet flower.
So, first thing you do is decide how big you want your bag and cut off the bottom, remembering seam allowances.
Now, turn your tank top inside out and pin to sew (I gathered mine a bit). Then sew. That's it! Now turn your bag right side out and add whatever other little things you want...
Such as a cute crochet flower, or buttons, or ribbon, or whatever. It's a nice light weight bag, perfect to put a few things in when you're going to the beach or something like that. :)