Fabric Substitute for Interfacing

Can I use fabric as a suitable substitute? All I have are cotton scraps - they wouldn't add stiffness but provide an extra layer? I am a newer sewist, so I only buy pattern and fabric for one project at a time. I have fabric and the Gallery tunic pattern, but don't have any extra interfacing. All the stores are closed. The national fabric/sewing chain is out of interfacing even when I try to order online.