I've heard it called a "planned indulgence" rather than a "cheat", but however you want to phrase it - it should be an intelligent decision/choice.

Make a plan and stick to it.

Don't go into the situation without knowing how to come out the other end.

I haven't done this, yet, and I am not sure what will happen when my birthday rolls around - I'll be in entirely a different situation - we are moving, likely in July we'll be driving right across the continent with two dogs and our son, so I'll be working hard to maintain this lifestyle and being forced to visit fast food establishments, so my birthday may come and go the following month, and I may be working on getting back on track, rather than planning an indulgence day.