There are a few different types of stitches that can be used on stretchy fabric, but the best stitch for stretchy fabric is the zigzag stitch. The zigzag stitch is a stronger stitch than a straight stitch, so it can handle the stretch of the fabric better. It's also a good idea to use a walking foot when sewing with a zigzag stitch, as this will help to evenly feed the fabric through the machine.