not to worry. You are simply experiencing heightened sensitivity.
This is why it's always been recommended (in the past, if possible, ) to be in a place that's very conducive to water fasting. Someplace with lots of good air flow.... sunshine everyday, etc.
The nauseated feeling will pass, and it is not like 'eating', though you might feel some grumbling, and so on.
Try not to subject yourself to spraying anything up close. Best to clear a room with something very natural, only real essential oils in water, and leave the room, while it takes effect.
Also, burn pure beeswax candles which purify the air.
I like to buy fresh flowers when I water fast.
We do the best we can. . . .
Just want to add, and emphasize, you will notice, more and more, that you will be sensitive to anything chemical or fake.
Remember, you are in some ways 'eating air'., and what's in it. And whatever you put on your body should be something you would be able to eat, if you were actually eating.