Someone requested that I make a guide on how to do this, so here it is. I'm going to be as brief as possible because this is really easy.
When creating bacteriostatic water, I go with the standard 0.9% benzyl alcohol to 99.1% water ratio. I wouldn't increase/decrease it without being more knowledgeable about what you're doing than I am in regards to solubility in benzyl alcohol (I wish I could find such numbers and post it here).
So without further ado...
1) Water - tap, or sterile (I use tap water and have had no problems with this but I recommend people research their tap water by reading the pdf your city/locale will put out on water quality before determining how safe it is to use). You also want to make sure you're not injecting lead - so if you are living in a building that has been around for a while, run the water for 2 minutes before collecting it. Even if you have a new building, the "lead free" pipes can still have a tiny amount of lead in it (yeah fucked I know...) so I recommend running the faucet for a while nonetheless.
2) Insulin syringe (needed to measure out the benzyl alcohol)
3) Vial of benzyl alcohol
4) Alcohol Pads (You need these to wipe down the vial tops)
5) Vial you're going to store your bacteriostatic water in. Self explanatory.
1) Use an alcohol swab to wipe off the top of your benzyl alcohol vial. Measure out an appropriate amount of benzyl alcohol (see examples below if you are bad at math).
2) After drawing out the benzyl alcohol, you can have this set aside.
3) Measure out the sterile water (if you have sterile water tubes from a needle exchange like I do, you don't have to measure it out) or collect the tap water, and put it into your vial you'll have your bacteriostatic water in.
4) Put in the benzyl alcohol.
100 units = 1 mL
1 unit = 0.01 mL
1 mL = 1 cc
To make 10 mL of bacteriostatic water, you need 9 units of benzyl alcohol (0.09 mL).
To make 30 mL of bacteriostatic water, you need 27 units of benzyl alcohol (0.27 mL).
To make 100 mL of bacteriostatic water, you need 90 units of benzyl alcohol (0.9 mL).