So we advise against the use of Sugar Soap as it can leave a film over the wall, creating a surface that the paint cannot stick to.
In some circumstances the paint can slide around on the surface and even peel away. Sugar soap can also leave a fine coating of sugar that may repel the paint leaving it patchy.
As our paint is water-based this potential hydrophobic reaction is something we want to avoid.
If the wall is washed down thoroughly so that there is no trace of the sugar soap, then this is still fine, it just generally ends up requiring more work than other alternatives.
We would simply advise to wash your walls with a little warm water and dish soap to prepare for painting.