Cook bacon until crisp; crumble and set aside, reserving hot bacon fat. Add chopped Brussels sprouts leaves to bacon fat; saute until browned.
Combine cauliflower, flour, beaten eggs, salt, and pepper; add enough soda water to make a thick paste. Drop rounds into hot oil fryer and cook until golden brown.
Top each fritter with dollop of sour cream, crumbled bacon, and sauteed Brussels sprouts leaves; serve immediately.