Cloth simulation, smoothing modifier and subdivision. Some sculpting for more smoothing and curling the edges because those were pinned in the simulation.
Settings for the cloth. A bit of negative shrinking gives more room for the negative pressure to really work, otherwise it'll be too taut.
Simulation with those settings, baked.
I don't know if this should even be called a sausage.
Blender cloth experimentation. Seeing and reading https://docs.blender.org/manual/en/latest/physics/cloth/introduction.html#springs really helped me to understand how the stiffness and dampening settings worked when words like "shear" made me think about something totally different. Not using any forces in the simulation, just what's found in the cloth itself.