spike (one's) drink
To mix alcohol or drugs into someone's drink without their awareness or permission. After several students began vomiting on the dance floor, it was discovered that someone had spiked their drinks. If you're at a bar or club on your own, you need to be wary of someone spiking your drink.
spike somebody’s ˈdrink
add (more) alcohol or drugs to somebody’s drink, without their knowledge: ...I discovered later that they’d spiked my drink. That’s why I was so ill!