I don't.
Seriously, I've been on this journey long enough to know myself - cheat days don't help me, they hurt. Sometimes a LOT. Most of the folks who fall off the wagon and regain their lost weight (plus some!) began with justifying one cheat meal or day, and then it became three, and then they couldn't find the motivation to get back on plan and stick with it.
So I don't do cheat days. I may have a restaurant meal, but I work it into my calories and it is still composed of allowed foods in sensible quantities. Or I have dark chocolate once or twice per day, but only 6-10 gram servings, depending on the bar.
I even ate off plan once, recently. After staying perfectly on plan for every major holiday I decided that I would celebrate my daughter's birth with a delicious cake and some Japanese (which I'd been missing and wouldn't normally work with my plan). But that wasn't a cheat, either. I intentionally allowed myself a period of no counting. I planned exactly what to eat, when it would end, and strategized how to get back on plan as quickly and painlessly as possible, all before a single bite entered my mouth. And I have done it once. Not every time a major bank holiday rolls around, or every weekend. Once every year or two - whenever a baby is born. That frequency is comfortable for me, and not beyond my ability to handle.
Now, your mileage may vary. Some plans are much more flexible than others (I'd argue mine is quite flexible every day, which is why I feel so little need to eat off plan - I always enjoy my food and am happy with what I eat
). Some more easily adjust for meals that won't contribute to weight loss. That may be what you mean, rather than cheat? Food isn't moral. It isn't good or bad. But the quantities we consume and the choices we make regarding how often and how much to eat something; those have a real effect on our bodies and it may not be what we want.
It's okay to eat something that doesn't get you closer to your goal every once in awhile, sure. But that's a choice you must make, and I caution that for the season of weight loss, in particular, infrequently veering off course is a better solution than planning in regular 'extras', which only serve to slow the process and may frustrate you more than just abstaining. Know thyself, we all have different tolerances in this area.
That's my best advice