Thanks for the question.

I have a couple of these plants myself.  They are quite striking with low maintenance.  However, they do not like having their feet wet for prolonged periods of time.  Long periods of direct sunlight can also have adverse effects on them.  Since you will be leaving them on a balcony, I’m wondering if you have a table and/or chairs on the balcony?  If so, just tuck your plants under them.  Another idea would be to get some ground cover cloth (this is the actual name – should be available at gardening centers) and extend it over the plant while it’s on the balcony.  This cloth will provide indirect lighting, will deflect some rain if it occurs, and will allow the soil to dry out should it get wet.

This plant can survive drought conditions for at least two weeks.  Since you will be gone for only a few days, perhaps you could just leave it inside and not put it on your balcony?

Here are a couple of sites that may provide you some further ideas:

https://www.gardeningknowhow.com/houseplants/snake-plant/snake-plant-care.htm

https://www.bhg.com/gardening/plant-dictionary/houseplant/snake-plant/

https://www.joyusgarden.com/sansevierias-aka-snake-plant-care/

https://www.thespruce.com/snake-plant-care-overview-1902772

Good luck!!