[Mr_Scripter]

pawn Code:

if(!strcmp(cmdtext, "//race", true)){
   if(!IsPlayerInAnyVehicle(playerid)){
       SetPlayerPos(playerid, 0.0, 0.0, 0.0);
       SetPlayerFacingAngle(playerid, 0.0);
       SetPlayerInterior(playerid, 0);
       SetPlayerVirtualWorld(playerid, 0);
   }
   else{
       new veh = GetPlayerVehicleID(playerid);
       SetVehiclePos(veh, 0.0, 0.0, 0.0);
       SetVehicleZAngle(veh, 0.0);
       LinkVehicleToInterior(veh, 0);
       SetVehicleVirtualWorld(veh, 0);
       PutPlayerInVehicle(playerid, veh, 0);
   }
   return 1;
}

without car

pawn Code:

if(!strcmp(cmdtext, "//tp", true)){
   SetPlayerPos(playerid, 0.0, 0.0, 0.0);//Change the Cords
   SetPlayerFacingAngle(playerid, 0.0);
   SetPlayerInterior(playerid, 0);
   SetPlayerVirtualWorld(playerid, 0);
   return 1;
}

Rep me if it helped

Edit the X,Y,Z cords
Not Tested