Why do people put Visine in drinks?

If you are referring to eyes drops, if swallowed they can cause serious illness even death.

"Commonly used drops marketed to reduce redness in the eyes typically contain tetrahydrozoline, which was approved by the U.S. Food and Drug Administration (FDA) in 1954 and belongs to a family of drugs called imidazoles. The chemical is found in Visine, Murine Plus, Altazine, Clarine and some other over-the-counter eye drops, according to Drugs.com. Constricting blood vessels in your eyes is how they “get the red out.”

The FDA considers the risk for these products to be low as they are labeled for external use only and are clearly marked “keep out of reach of children.”

What happens if you drink eye drops?
Intentionally or accidentally drinking eye drops can lead to toxic blood levels. When used in the eyes as directed to reduce redness, these types of eye drops are not absorbed systemically in amounts that lead to toxicity.

When consumed orally, tetrahydrozoline passes quickly through the gastrointestinal tract, rapidly reaching the blood and the central nervous system.

Symptoms of an overdose of tetrahydrozoline include drowsiness, slow breathing or absence of breathing, slow heartbeat, hypothermia and possibly even coma."

Source: American Academy of Ophthalmology