Final answer:
Caffeine is the most widely used drug substance in the world, found in common beverages such as coffee and tea.
Step-by-step explanation:
The most widely used drug substance in the world is caffeine. Caffeine is found in many common beverages, such as coffee, tea, and energy drinks. It is a stimulant that affects the central nervous system, providing a temporary boost in alertness and energy. Many people consume caffeine on a daily basis to help them stay awake and focused.
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