The odor comes from the sulfamic acid which is the building block of the formula. Without sulfamic acid there is no Flex Ice as other acids turn the powder into a brick. We tested over a dozen fragrances in the formula with only one that did not sour over time or create re-soil issues. We have sold Viper Renew for over a decade and as a pre-spray has a very strong acidic odor without complaints. Rug plants use acetic acid which has a sharp vinegar smell. Most acids have odor issues so I have always been surprised by the concern of the odor at a 1 to 640 dilution, especially when used to rinse pre-sprays with fragrance. The odor is what it is and we have done what we can to mitigate. Many fragrance deodorizers are sold in the industry so adding a small (do not create a re-soiler) amount to the head pack when you mix it up is one solution (choose one to complement your pre-spray fragrance). The other solution would be to enhance the fragrance of your pre-spray which should be able to last long enough until extraction.
We sell 16 rinses in our system and after 2 years more Flex Ice ready to use gallons are used than any of the other 15 that have been sold for years. Apparently the benefits have outweighed the negatives of the odor and the need to use with soft water. I talked to one cleaner who lived in a hard water area who loved the Flex Ice but had some sediment issues. Once he realized the issue was hard water he immediately ordered 2 water softeners for his 2 trucks because he did not want to clean without it. I heard that many cleaners love Flex Ice because they can use for their restoration jobs and for their delicate upholstery cleaning. In short, for many it is the only rinse that they need. Of course if you need another one I have 15 choices for you.