Caffeine (and other ingredients such as guarana) will boost BP for a few hours, as will tobacco use (but for a shorter time frame). But if it spiked off the charts there is a probability his BP was already elevated.
Caffeine: How does it affect blood pressure? - MayoClinic.com
Rick is on the right track. Have your guy get a BP check before blaming the juice.
Caffeine: How does it affect blood pressure? - MayoClinic.com
Rick is on the right track. Have your guy get a BP check before blaming the juice.