A destroyed car takes about 3 seconds to respawn in Rocket League.
A demolition removes the car from play, then returns it at a respawn point on its team’s side of the arena. That short delay is long enough to create a temporary numerical advantage without keeping a player out of the match for too long.
The respawn is not the same as merely being bumped, flipped, or disabled: only a demolition triggers the destruction-and-return sequence. Demolitions generally occur when a supersonic-speed car strikes another car, while a head-on collision can destroy both vehicles. The attacking car survives only when the impact conditions favor it.
Later updates changed the camera transition and added more control over where a player respawns, but they did not turn the standard delay into five, four, or two seconds. The three-second timing remains the conventional answer used in Rocket League rules and gameplay references.