Our world needs to be more environmentally aware. That's why I avoid using plastic in the shop. But people associate cold drinks with clear cups, so the only solution I found was to use PLA compostable plastic. PLA stands for polylactic acid. Lactic acid is made from the dextrose (simple sugar) in the starch collected from corn, then transformed into poly form (longer chain). It turns corns into plastic cups and is compostable under the right conditions in 90 days.
A big downside is these cups melt when you put liquid above 45℃ in them. So I have to be make sure I cool down the drink before putting it into the cup.
For those interested,