I really like substitution recipes, but my plan makes them quite decadent (yay low carb!) which makes adherence a pleasure. That said, I will allow a serving of a sugary food like sweet potatoes or even a piece of pie, but NO seconds. Given then we usually do this with family that brings most of the food, it makes it trickier than if I could cook it all myself, but it is still very doable. There's plenty of on-plan options for me, but a controlled amount of something else is acceptable. The trick is getting right back on plan immediately afterward, which I've gotten better at over the years