Glass (silicon oxide) is sourced from two types of places on Earth:
Quartz mines featuring large white colored boulders.
Sand deposits.
The quartz mines are sometimes mined more often than the sand deposits. In any event, large machines powered by diesel fuel engines, are used to move massive amounts of raw material from one place to another.
People work long hours driving trucks full of mined quartz to factories where the quartz is ground into dust, refined (some impurities are removed) and the quartz is melted melted and molded into water tumblers and other drinking glasses.
People living in affluent societies use these glass drinking vessels for drinking beverages.
Relatively speaking, what is more "green", environmentally friendly, or sustainable in the long-run:
Buying food (spaghetti sauce, olives, strawberry jam, salsa, etc...) in glass jars; throwing glass jars into a recycling bin; and buying water glasses from a store.
Buying food (spaghetti sauce, olives, strawberry jam, salsa, etc...) in glass jars; re-using glass jars for water; and never buying water glasses from a store.