They could use the Euro Bottle or NRW Bottle refill glass bottles, that a lot of European countries ate using. They're being refilled 12 times on average.

I don't like cans because the drink gets so hot so fast, it isn't insulating at all, but in general don't buy individually packaged anything. Lots of glass bottles of booze and wine, but much less "turnover" that way, a few a month. Water from the tap, fancy water we have a Lifestraw pitcher in the refrigerator (tap water is safe here but the filtered cooled water is delicious). Bring an empty water bottle to concerts, or the sealed liter bottle (whichever is allowed).

So not none, still a few here and there, now and then. But mostly just try to avoid anything packed for individual servings.