So energy drinks are op in a stupid way. Honestly it wasn't a good idea to add something that give better speed for human classes. Right now, if you are buffed by this, all you need is some brain to dodge every incoming attack. On top of that you can almost outrun spitters and are completely invulnerable to ceratos and carnos.
So here are the ideas to make it still useful, but not op:
-Instead of speed buff, make it give infinite stamina for sprinting
-Reduced stamina consumption for heavy melee
-Faster melee attacks and faster weapon switching (both like 25% faster)
-Make it give full dilo stamina drain protection