Tubilad is trending in Tel Aviv. The Twitter hashtag is applied to all nights in the city that start with a shot of Tubi 60, the lemon and herb-flavoured liquor sold only in Israel.

Created in the small coastal city of Haifa, the cloudy drink first appeared in the capital in 2013 and since then, Tel Aviv has been hooked. As well as its own hashtag, Tubi 60 has t-shirts that proclaim the wearer's love for the stuff and a Facebook appreciation society.

Which is curious, because nobody really knows what Tubi 60 contains.

"Israel is a very small country," says Jacob Rosthchild, a 27-year-old marketing manager from the UK who moved to Tel Aviv three years ago. "It's a bit like someone offering you a drink brewed in Wolverhampton. It's not like you're going to go to Wolverhampton yourself and look for it—you just kind of think, Meh, OK, I'll try it."

An English translation of the Tubi 60 label rather unhelpfully notes only that it is a 40 percent-alcohol "made with lemons, herbs, flower with tree extracts, specially designed for a refreshing, uplifting, and pleasurable experience." Bars who serve it refuse to share what they know, and at the time of writing, I haven't been able to get a straight answer out of its creators. We've been emailing back and forth for months.

Not that any of this has stopped Tel Avivians from chugging Tubi by the bucketload.

I meet Rosthchild in Kuli Alma, his favourite Tel Aviv nightclub and also a place known for championing the Tubi phenomenon by serving not just shots of the stuff, but Tubi and tonic cocktails and even a syrupy Tubi slushy.

It's only Wednesday but the place is packed. People lounge on the stairs that lead down into the leafy open-air courtyard, from which an art gallery, a lounge, two small bars, and a pulsating neon purple dancefloor splinter off.

I'm sitting on an upturned crate chatting to Jacob and an achingly cool DJ from New York who is in town en route to Berlin. She suggests we order some Tubi to get the party started. My immediate thoughts? It tastes like paint stripper. Paint stripper mixed with a hint of lemongrass and maybe something like washing up liquid. And yet I feel strangely compelled to have more than one shot.

Rosthchild and I pass the balmy evening drinking Tubi slushies. I chat to Muslims and Jews, locals and travellers from all over the world. I haven't felt this mellow since the days of smoking joints on my threadbare couch at uni and before I know it, I'm buying my own bottle of Tubi to take home.

The next day, the liquid appears to have separated, a thick yellow sediment settling at the bottom of the bottle. It's looks highly unappetising but people—myself now included—seem to love it.

"There's a rumour that it uses extract of the African khat leaf," Rothschild had told me at Kuli Alma, "which kind of rings true for me because I think it has a kind of euphoric effect, similar perhaps to ecstasy."

Some even say that a night on Tubi won't result in a hangover, making it even more appealing to the masses who drink it every weeknight here. From my own experience, I can't say that this rings true, but I did feel a different kind of drunk on Tubi. The kind that makes you crave more.

"While it is flattering to have people speculate about how Tubi gives such a great effect, the fact is, there is no khat or anything like it in the ingredients," says Tubi CEO and co-founder Hilal, who after several months of negotiating, agrees to talk to me about his creation. "Tubi has been certified and approved by the Israeli Ministry of Health since day one, thus all the ingredients in Tubi are compliant with the Israeli, European, and US standards."

Hilal tells me that he and his business partner came up with a recipe for a new alcoholic mixer and started selling it to friends. Some clever marketing via Facebook and Twitter combined with snubbing the mainstream media resulted in an exclusive and highly desirable product. Once the "hipsters" got involved, Tubi's popularity skyrocketed.

"So, when can we buy it here in the UK?" I ask.

Hilal's answer is evasive: "The first shipment is due to go out next month, maybe to Panama, maybe somewhere else …"

He does, however, tell me about a particular delivery of Tubi he made to a party in Tel Aviv shortly after the drink landed here.

"One of the most memorable was Israeli Independence Day in 2014," he says. "My brother and I got a call to make a nationwide 'emergency' delivery of Tubi and found people standing in line waiting for the bottles to arrive, and at each liquor store we dropped boxes off to, there were more people waiting! This was unprecedented."

The story seems far-fetched and yet it in a city like Tel Aviv, it somehow makes perfect sense. During my time here, I meet Americans, Brits, Swedes, and Germans throwing back shots of Tubi together and declaring their love for the city, as well as its curious drink.