I made this sweet and sour cauliflower as a vegan alternative to sweet and sour chicken. I actually like it a lot better this way. The battered cauliflower is firm and meaty enough to give a satisfying mouthfeel and kind of juicy because of the moisture in the vegetable. If you use a fresh cauliflower, the taste is also quite neutral and not at all cabbagey.
To create a firm, crispy layer on the cauliflower, you need to deep-fry the cauliflower florets twice. The first fry to soften the cauliflower and the second fry to crisp up the batter. The same reason why you double fry potatoes.