>>21655240
Military Energy Gum is the classic and depending on where you buy it from is around 20-30 cents per 100mg piece, but there're plenty of no-name brands that work just as well - caffeine is such a dirt cheap ingredient you generally don't have to worry about getting scammed. "Maax" is one of those no-names with 125mg/piece for roughly the same price per piece. They all taste the same, which as mentioned is generic mint (or cinnamon if you so choose) fading into the bitter taste of caffeine.
Pure caffeine pills are even cheaper (~5 cents per 100mg), they just taste absolutely horrible and can be hard to swallow depending on both how they're made and how you personally handle pills.
I haven't tried the Costco shots though, unfortunately, so I don't know if they're any good.