Hello!
It would be awesome to have the possibility to find coffee which you could brew in a pot and fill up in canteens or waterbottles. This shouldn't give you endless indefinitely but lower the speed of the decline of your stamina.
Lets say you can sprint 20 seconds till your character gets exhausted, it will take now 28-30 seconds till your character gets exhausted. You could add as well that the recharging time goes down, so your stamina goes up faster. You guys would need to find the sweet spot there.
A full PET-Bottle of coffee should last at least for 2-3 minutes, a stimshot at the moment lasts 1 minute and gives you indefinitely speed, should be fine to have this effect for at least 2 minutes.
The energydrink should have the same value but is rarer to find maybe?
"Why would this addition be good?"
For long travels where you know that you need to run some time this addon would be nice.
In combat situations this would be a good addon too, you might see somebody running in the distance but you can't catch up? Drink some coffee and have a slight advantage. Somebody shot you from somewhere and you want to flee? Drink some of the coffee and get an advantage in the escape.
Furthermore: The aspect of finding consumables is something nice to have. You might be hoarding these things if you got a base, but you are always consuming them at some point. It is something valuable to find and at the same time its not.