Those 3 plus years, I was so proud of
Then I threw them all away, for two Styrofoam cups

from Macklemore and Ryan Lewis (Ft. Ben Bridwell of Band of Horses & Macklemore) – Starting Over Lyrics on Rap Genius

Meaning

Macklemore had been clean from the cough syrup, also known as lean or purple drank, for over three years before relapsing. Usually lean is consumed with two Styrofoam cups, there could be multiple reasons for this:
To prevent others (mainly police) from seeing the purple through the Styrofoam.
To keep the liquor and the cough syrup separated.
-Or, the most logical explanation (in my opinion), to prevent the drank from slipping out of your hands. Lean tends to “sweat” through the first cup.

However, based on this interview, it looks like he drank two bottles in two separate cups, on two seperate nights.

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