There is no definitive answer to this question as the caffeine content in coffee can vary greatly depending on a number of factors, including the type of bean used, how it was roasted, and how it was brewed. That being said, there are some general trends that can be observed when it comes to canned coffee and caffeine.
In general, darker roasted coffees tend to have more caffeine than lighter roasts. This is because the longer the beans are roasted, the more of their natural caffeine is cooked out. So, if you're looking for a jolt of caffeine from your canned coffee, opt for a dark roast over a light roast.
Brewed coffee generally has more caffeine than instant or percolated coffee. This is because brewing extract more of the beans' caffeinated oils than other methods of preparation. So, if you want maximum caffeine from your canned coffee, look for brands that brew their coffee before canning it.
Finally, Arabica beans typically have less caffeine than Robusta beans. Arabica beans are what most specialty coffees are made from and they tend to have a smoother flavor than Robusta beans. However, they also contain about half as much caffeine as Robusta beans.