[xRyder]

That's because you use loop. And your looping through all vehicles.
Try this code:

pawn Код:

if(strcmp(cmd, "/destroycars", true) == 0)
{
    if(IsPlayerConnected(playerid))
    {
        if(IsPlayerInAnyVehicle(playerid))
        {
            new vehicle = GetPlayerVehicleID(playerid);
            if(PlayerInfo[playerid][pAdmin] < 1340) return SendClientMessage(playerid, COLOR_GRAD1, "Niste ovlasteni da koristite tu komandu!");
            DestroyVehicle(vehicle);
            SendClientMessage(playerid, COLOR_GREY, "Vozilo je unisteno!");
        }
    }
    return 1;
}