I have seen this story:
The former Pope was walking across St Peter’s Square when a group of Argentinian Catholics came up and offered him a drink of maté (an Argentinian caffeine), which he proceeded to consume at pace. The Swiss Guards (security detail) were appalled, and told him that the drink could have been poisoned. He is supposed to have replied, “I wasn’t worried at all. They were pilgrims, not cardinals”.