The Brief: Formerly a slang term for Quaaludes, Disco Biscuits is now a nickname for ecstasy.

DEEP DIVE
The term disco biscuits originated as a reference to Quaaludes when they were popular in the 1970s and at discos.
Quaaludes are no longer manufactured, but ecstasy, a party drug is sometimes referred to by the same name (disco biscuits) because of its popularity at concerts and raves.
What a weekend I had in Dumfries never drank alot so was a bit sober and I enjoyed laughing at all the people on the disco biscuits with their jaws swinging more than their arms
— Andy (@pandymccubbin) March 17, 2019
Someone high on disco biscuits is said to be zooming.
i’m craving those party rings or disco biscuits idk what ever tf they’re called but i’m craving them
— shauna (@shaunamccann) March 18, 2019