Which character's favorite drink is Nehi brand grape soda?

Radar O'Reilly's favorite drink is Nehi brand grape soda.

Walter “Radar” O’Reilly is the young company clerk of the 4077th MASH, played by Gary Burghoff. The grape soda is one of the details that emphasizes Radar’s homespun, youthful personality amid the camp’s adult drinking culture and grim medical work.

Nehi was a real American soft-drink brand that sold fruit flavors including grape, orange, peach, and root beer. The name is commonly misheard as “knee-high,” but the brand is spelled Nehi. On M*A*S*H, the drink is repeatedly treated as Radar’s signature refreshment rather than an alcoholic beverage.

The association appears in plot moments such as “Fallen Idol,” when Radar’s Grape Nehi is contrasted with Hawkeye’s beer, and “The Winchester Tapes,” in which Charles Winchester offers Radar a case of it. Frank Burns, B.J. Hunnicutt, and Maxwell Klinger all belong to the same ensemble, but none is identified as the show’s Nehi devotee.