The survey website www.14to42.net asserts that this sign "very likely belonged to the Holiday Coffee Shop, located here from 1959 to 1972." The different colors of lettering suggest a "soda lounge," which has a clubby ring — and, nowadays, an alcoholic one, as in "whiskey soda" or "scotch and soda." My guess, though, is that this was the sign maker's innocent shorthand for "soda fountain," which at any decent size wouldn't fit.
Surviving painted "lunch soda lounge" sign
23 West 35th St. (Fifth-Sixth Aves.)