Step 1:
Fold and cut a large paper square in half or glue two smaller squares together. Both papers are the same size.
Prefold the purple paper in half and fold both edges to this prefolded centerline.

Step 6:
Fold over these lines, use the prefolded squares pattern as guidance.

Step 5:
Fold over these two prefolded lines.

Step 2:
Fold to the centerline again and unfold the model.

Step 4:
Fold both edges to the centerline two more times and unfold the model afterwards.

Step 3:
Prefold in half and fold both edges to this prefolded centerline.

Step 10:
And the bottle is done....

Step 8:
Fold into a straight angle (90 degrees).

Step 9:
Fold into a straight angle and glue the edges together.

Step 7:
Fold the left and right part into a straight line with the centerpart.

Step 16:
Repeat step 15 three more times and glue the edges together.

Step 15:
Fold the square on the right on top of the square on the left, see arrow.

Step 12:
Prefold in half and fold both edges to this prefolded centerline.

Step 11:
Prefold in half and prefold both edges to this prefolded centerline.

Step 14:
Fold over these two prefolded lines.

Step 13:
Fold to the centerline and unfold the model.