This is one of the first Ghosts I tried and is one of my favorites of their lineup. Not my absolute favorite (that title belongs to Welch's Grape) but definitely up there.
The citric acid in the Warheads Sour Watermelon is overwhelming but in a way that complements the Warheads branding. Before you taste the acid there is a brief but pleasant taste of watermelon or cherry. Beyond this I can't discern what it tastes like other than citric acid. It's very sour. It could be traumatizing if you're not ready for it. On an empty stomach this would probably kill you.
Being so chemical-forward this drink is not refreshing, it's something to enjoy on its own for its own sake. It's great that it lacks sugar because that makes it taste very clean and light and it does not linger long.