We go through this process every season. I find it takes about three our four good flushes of the system to clear the anti-freeze taste out. Our water tank is SS.
We also have an activated carbon inline filter. It helps remove some of the anti-freeze taste (we did a test last year), but flushing eventually clears the taste.
Try draining the tank, then fill the tank and add about 1 cup of chlorine bleach, the unscented kind, for every 40 gallons of capacity, then flush the system completely. Then take 1 dry cup of baking soda for every 40 gallons, dissolve the baking soda in hot water and add it before you fill it and flush it again. That should take out all the odors, smells, tastes, gunk and so forth, it works in stainless steel, aluminum, or any other type of tank. If it is really foul and smelly you can run the chlorine through it twice, and the second time you let it stand 24 hours.
Chlorine is a highly unstable molecule and breaks down very quickly into inert compounds, does not stay in the system long enough to do any damage at all, and will kill every type of virus, bacteria, or micro organisms in the tank. Trust me, if you have something in the tank that bleach won't kill you have bigger problems than some odors. The baking soda will remove the chlorine smell and bad taste, and if you think you need more than one cup in the one gallon of hot water, just make sure you dissolve it and put a bit more.