San Francisco city leaders are united in an effort to slap a tax on soda, energy drinks and other sugary beverages. The only questions left are when and how. The backers of two separate efforts to place a 2-cents-per-ounce levy on drinks with added sugar announced plans to go forward together on Monday, with backing from medical experts from UC San Francisco. Supervisor Scott Wiener was the first to introduce a soda tax proposal last month. Not long after, Supervisor Eric Mar announced a competing ballot measure.

Their proposals are “very similar,” they admitted Monday — and the final version to be presented to voters, with the backing of supervisors John Avalos and Malia Cohen, will likely have elements of both.

Up to $31 million could be collected annually with a 2-cents-per-ounce tax, which would be paid by beverage distributors on the wholesale level.

That cash would then fund nutrition and recreation programs in the schools, provide cash for community nonprofits, and help reopen shuttered Recreation and Park Department clubhouses.

Consuming too much sugar has “addictionlike consequences,” and is a cause of non-alcoholic cirrhosis of the liver, said Dr. Laura Schmidt, a professor at UCSF’s medical school.

Similar to levies on cigarettes, a soda tax would lead consumers towards healthier choices and spread awareness of its harmful health effects, Mar said.

The soda tax would have to be approved by two-thirds of city voters at either the June or the November ballot.

The American Beverage Association — which spent heavily to defeat a proposed taxes on soda in Richmond and El Monte last year — would likely funnel millions into San Francisco to beat back this tax as well.