Aspects of the disclosure relate to fluid injection systems, apparatus, methods, and associated components thereof that include flexible hoses for wellhead sites. In one implementation, a fluid injection system for wellhead sites includes a pump, a pump manifold, and a flexible hose coupled between the pump and the pump manifold. The flexible hose includes a first end coupled to the pump and a second end coupled to the pump manifold. The first end of the flexible hose includes a first end fitting coupled to the pump, and the first end fitting is oriented at an angle relative to a horizontal plane. The second end of the flexible hose includes a second end fitting coupled to the pump manifold, and the second end fitting is oriented vertically and perpendicularly to the horizontal plane.