Tonic, noun: one that invigorates, restores, refreshes, or stimulates; medicinal

Source: https://www.merriam-webster.com/dictionary/tonic

We read this word in chapter 9 of Quicksand. Helga uses it in the context of needing something to cure her malaise with New York and how she begins to hate it.

“As the days multiplied, her need of something, something vaguely familiar, but which she could not put a name to and hold for definite examination, became almost intolerable. She went through moments of overwhelming anguish. She felt shut in, trapped. “Perhaps I’m tired, need a tonic or something,” she reflected. So she consulted a physician, who, after a long, solemn examination, said that there was nothing wrong, nothing at all. “A change of scene, perhaps for a week or so, or a few days away from work,” would put her straight most likely.”