Gillywater was a wizarding beverage, that was sold in the Three Broomsticks Inn in Hogsmeade, and the Leaky Cauldron in Diagon Alley.

What does Gillywater taste like?

The actual Gillywater is a lot like flavored water, with extras on the flavor. It's like a sucker punch of lemon right at the end. It was the color of lemonade, but so not like lemonade.

What is Gilly water at Universal?

Basically, Gillywater is just bottled water, but Eternelle's offers four colored, flavored "elixirs" that it will pour into your bottle of Gillywater. ... The little bursts of blueberry flavor helped highlight the brightness of the mint, giving the drink a unique and refreshing taste.