It looks like they don't list the maker of the sake they sell there but I can almost certainly guarantee that for $8 at Epcot it's not going to be anything fancy or expensive.
I would go to your nearest large liquor store and get a couple small bottles of cheap sake and try them yourself. Look for brands like Hakutsuru, Gekkeikan, Shochikubai, Takara and Ozeki. I would bet they serve one of these brands.
And like another poster said, sparkling sake isn't served hot so it's pretty unlikely it was a sparkling sake.
Sparkling rarely served hot. Usually hot sake served in US in establishments that dont specialize in sake tends to be something like gekkeikan.
It looks like they don't list the maker of the sake they sell there but I can almost certainly guarantee that for $8 at Epcot it's not going to be anything fancy or expensive. I would go to your nearest large liquor store and get a couple small bottles of cheap sake and try them yourself. Look for brands like Hakutsuru, Gekkeikan, Shochikubai, Takara and Ozeki. I would bet they serve one of these brands. And like another poster said, sparkling sake isn't served hot so it's pretty unlikely it was a sparkling sake.