"The glass and the orangeade."
Translation:Το ποτήρι και η πορτοκαλάδα.
Because πορτοκαλάδα is a grammatically feminine noun, so it needs the feminine article η and not the neuter article το.
Nouns in Greek can have one of three genders: masculine, feminine, or neuter. The article to use and the endings of adjectives will depend on the gender of the noun they are used together with, so it's important to learn the gender of nouns.
Fortunately, you can usually tell the gender of a noun from the ending; for example, pretty much all nouns that end in -α in the base form but not in -μα are feminine -- including πορτοκαλάδα.