Trace around the jar bottoms onto felt scraps and cut out circles just inside the traced lines; set aside.
Cut sweaters into rectangles long enough to wrap around the jars and wide enough to extend at least 1 inch above the jars. Plan for a finished edge at the top and consider whether you want to roll a cuff over at the top when you decide the dimensions of the sweater rectangles. Sleeves and bottom ribbed edges of sweaters work nicely for top finished edges. With right sides together, stitch the ends of each rectangle together with a 1/4-inch seam allowance to make tubes; turn right side out. Some sweaters may have sleeves that are just the right size to slide over a jar; in those cases, cut tubes from the sleeves.
Insert jars into the sweater tubes. Turn the jars upside down. Using a double strand of sewing thread, sew around the cut edges of sweater tubes using large basting stitches. Gather edges together around the bottom of the jars. Knot ends to secure.
Glue felt shapes onto the jar bottoms over the gathered sweater edges; let dry. Turn jars upright and embellish with a crocheted yarn tie, and, if desired, a jingle bell hanging from a single yarn. Put candles into the jars.