Valerian root tea

From Memory Alpha, the free Star Trek reference

Valerian root tea is a type of herbal tea made from the root of the valerian plant (Valeriana officinalis), native to Earth.

Deanna Troi ordered a hot cup of valerian root tea in 2369. (TNG: "Second Chances")

In real life, valerian preparations have a mild, non-addicting sedative effect, and thus the herb is commonly used in herbal sleeping aids, including teas, capsules and liquid extracts.