A warp core breach was a beverage served in Quark's on Deep Space 9. The drink was prepared in what looked like a large fishbowl and effervesced, emitting a large amount of foggy gas from the top of the bowl.
Quark once began to prepare one for Julian Bashir after he mentioned that he felt tense, stating that one sip of it and the Doctor would be relaxed for the next three days. After one look at the bowl overflowing with fog Bashir decided he wasn't that tense, and Quark never got around to adding the rest of the ingredients. (DS9: "His Way")