#mixing stimulants (caffeine) with depressants (alcohol) is seriously a bad idea

[21st-century-minutiae]

"Spiked" is a euphemism for "contains alcohol." Specifically, it refers to adding alcohol to normally non-alcoholic beverage products. There is usually a connotation that the alcohol was added secretly without the knowledge of witnesses (or other consumers), such as someone 'spiking the punch bowl' at a public gathering, but many products are sold explicitly as 'spiked' (see the above).

Alcohol is quite popular, though there are many legal restrictions on its distribution.

A similar word to refer to 'alcoholic beverage that isn't always alcoholic' is 'hard.'