San Francisco officials are deciding whether to impose a warning on ads for a favorite drink of children and a bane of public health advocates: Sugary soda pop. The "Sugar-Sweetened Beverage Warning Ordinance" would require health warnings on advertising within city limits — on billboards, walls, the sides of cabs and buses. Supporters and opponents say San Francisco would be the first place in the country to require warnings on ads for soda, which is linked to rotting teeth and obesity.