1.5 bags are mylar, same as fancy birthday balloons, but heavy duty. Unfortunately they aren’t recyclable, but if you’re doing 100% Soylent 1.5 for all food intake, considering the volume of a flattened empty bag, it would take months, maybe years, to fill up a standard kitchen trash bag provided you squished it down now and again. Waste is the least of anyone’s concerns with 1.5, so maybe that’s the way to go.
That said, 2.0’s bottles are recyclable top to bottom except for the seal. Glass would have this advantage also, but it’s far heavier, which increases shipping loads, which contributes directly to atmospheric CO2. Aluminum is light, but extraction is more resource intensive than plastic production. As it is, I can’t say there’s anything else I eat that provides a balanced meal and has near-total recyclable packaging. It might be inefficient to ship water, but it’s way more efficient than most food out there.
Ideal solution: municipal soylent supply. @rob has written about this somewhere if I remember right. Get on it, folks!