The shape is predetermined, but would depend on the exact crimping used - which would affect the shape of the base and the way the lower edge of the sides starts out. Foil packs are constructed slightly differently from purely plastic ones. Also the material of the packaging affects the way it flexes (and possibly stretches under pressure), which also affects the shape. I would assume an open top, so that the liquid can be poured in; a sealed top would mean the need for a hole through which to inject the liquid, and that could affect the structural integrity of the packet.
May 14 2021, 5:12 PM
What I believe is that we need more information to make accurate calculations, as the shape formed is not a precisely-defined one. (Even if we had that information, it looks to me as if we would need to solve a differential equation of some complexity to take all the factors into account, as the different portions of the surface have different constraints.) Or you could cheat and use a Pringles container - that one is easy.