The temporary power drug used in Season 3 of The Boys is Temp V. Its in-universe designation is V24, but the characters and marketing primarily call it Temp V because its powers last only for a limited time.
Temp V is a modified version of Compound V, the substance Vought uses to create permanent superheroes. Unlike standard Compound V, which is generally administered during childhood, Temp V was developed for adults and temporarily gives them superpowers for roughly 24 hours. Billy Butcher and Hughie Campbell use it while trying to fight Homelander and investigate Soldier Boy.
The drug does not grant everyone the same ability. Butcher develops heat vision and enhanced physical abilities, while Hughie gains teleportation. Other users can manifest entirely different powers, reinforcing the show's idea that Compound V's effects are unpredictable.
Temp V is not the same as ordinary Compound V, V-Rush, or V24 as a separate drug: V24 is the laboratory designation for Temp V. Repeated use also causes severe neurological damage, making the supposed shortcut to power increasingly dangerous.