You could try in Sculpt mode with the Cloth brush (not easy to handle imho).
You could also use the Cloth > Pressure feature, first create a vertex group that you'll pin:
Then give your object a CLoth simulation with Pressure (more than 0), play the animation, it's going to inflate except where you've pinned:
At the end you can use the Cloth Filter brush > Pinch option to get that:
You could also project a aluminium-like image texture on your pack:
Then subdivide your object and give it a bit of volume with the sculpt Draw brush for example (also Draw Sharp and Crease), Ctrl to invert the effect, Shift to smooth: