I saw this at a friend's house. A sewn happy birthday banner. I had to make a few.
Just cut out 15 triangles each of two kinds of fabric. Cut out letters or paint on with fabric paint. I used double sided iron on interfacing to get the fabric letters on the triangles.
Then I sewed them around the edges to make them secure.
Then sew two triangles of scrap fabric together leaving the top open. Turn right side out and pin bias tape to the tops of each triangle in order and sew on each side. Leave enough on the ends to hang up.