The optimal time to drink caffeine is about 90 to 120 minutes after waking up. This delay helps to avoid the afternoon crash and provides a consistent arc of energy throughout the day. It's also beneficial to limit your last caffeine intake to around 2:00 p.m. or 3:00 p.m. to avoid disrupting the architecture of your sleep. If you're planning to exercise in the morning, it's okay to have your caffeine before the workout, but be prepared for a substantial dip in energy in the early afternoon. If you're not a regular caffeine user, it's best to avoid it before or after exercise as it can increase core body temperature and constrict blood vessels.