A flexible pouch having a removable cap for use with the tube spout fitment and a method of filling the flexible pouch is provided. The removable cap is formed from a tube of pliable material, and has a first opening and a second opening. The first and second openings each have a peripheral edge. The peripheral edge of the first opening is configured to engage the outer surface of the tube spout fitment. The peripheral edge of the second opening is pressed onto itself and sealed so as to form a flattened edge. The method includes the steps mounting the removable cap onto the tube spout fitment. Filling the pouch, and sealing the second opening of the removable cap so as to form a flattened edge.