Odor control in outdoor tent

I'm growing four plants outdoors in a pergola tent and the smell is getting pretty bad and I think neighbours might be getting curious as to what's in there! That's before they have even flowered! Is there anything I can do about the smell? The tent is 3m x 3m (118 inches). I'm living in rented accommodation so don't want anything that will make the electricity bill rocket! I'm not living in the US so if anyone suggests an online company, it would need to be one that delivers outside the US. Thanks in advance.

:hippy: