The findings of research show that brain training improves the brain's ability to do the specific task of the exercise. Brain training does no increase intelligence nor improve memory.

It may help some lazy skills to work better. As one focuses on the exercises, one might develop better skills at focusing on a task.

My memory and cognitive abilities have remained in the same weakened state for over 13 years but I can do brain training and consistently improve my scores.

So, if you want to get good at Sudoku, play it often. Mental stimulation is always good because it causes blood to flow through the brain.