Supa Yum was a soda brand before the Great War.
Apparently, according to the label, it is fruit-flavored. The lack of mention of the drink would imply that it was at least not as popular as Nuka-Cola or Sunset Sarsaparilla.
Supa Yum bottles appear in Fallout: New Vegas under the form of hydras. The soda bottles hydras use are Supa Yum bottles.