Logorrhea

A product of Weasley's Wizarding Wheezes, the beverage known as Logorrhea is a fizzy drink with surprising truth-potion type qualities. It is sold in small vials, but also a large jug. It was released in 2006.

As advertised, it's "Not Veritaserum, But It Might As Well Be!"

One swallow will cause the imbiber to speak brash truths in garish ways. It's affects can be resisted by the exceptionally self-aware. But caught unsuspecting, the result is comical and sometimes embarrassing. After a few minutes the effects of just one swallow will wear off.

At Absit Omen

Figaro buys some at Spellpunk: [1]

Figaro Sellaphix brings some to a party in the Room of Requirement: [2]