Assuming they are the standard 8oz cans, it’s only 160 mg of caffeine and 220 calories. It’s hardly a dangerous drink. A decent size cup of coffee has about the same amount of caffeine.
I drink a coffee or a Red Bull before almost every run and sometimes a gel with caffeine during a long run. It absolutely helps performance, at least for me.
I’ve been drinking Red Bull fairly regularly (3-4 per week) for over 20 years, and I am in great health. Blood pressure is perfect, BMI of 20, RHR in the high 40s.
In the past few years, I switched to more coffee than Red Bull to cut down on the sugar.
If he was drinking 2 Redlines or 2 16 oz Monsters, that would be a little more extreme.