The peak "redbull-stockpiling" was "so we'd have stuff for later" or "for the office/truck/etc." I've certainly consumed 1g/day of caffeine fairly often. The biggest problem is once you get to that level, you need to hydrate (and...dehydrate) constantly, starting about an hour later, for hours.
Most people wouldn't get the 4 meals a day served (breakfast, lunch, dinner, midrats) all at DFACs. I usually ate once or twice a day in the DFAC, and in the summer, especially if you didn't have a physically demanding job, it was hard to even want to eat once a day in 100-120F heat. I often ended up reverse-cycle so had dinner for "breakfast" and then maybe went to midrats or maybe didn't, usually was too busy.
Coffee from "green beans" (the starbucks knock-off) with a total of 6 shots of espresso into a regular-sized paper coffee cup worked pretty well, too -- I could leave the cup in my truck for a few hours and in 120F inside a closed car it would stay rather hot.
It was pretty amazing to me how different things were at different times/places within the war. There were huge bases (where I nominally lived) with 5mph speed restriction (you could actually be pulled over and ticketed; I was once!), strict "you must wear your reflective belt" policies, multiple swimming pools, world-class hospitals, almost walmart-sized PXes, on-base vehicle registration, etc. There were guys living 6-12 in a house out in the country, and people on long range patrols in trucks and (rarely) dismounted, etc. And everything in between.