Over the past few years my husband changed what he was eating with cereal because grapes required being able to count he thought and eating a whole banana was simpler. I tried to explain that sliced almonds and grapes are better fiber choices with whole grain toast too.
I made a big sign on the kitchen island declaring bananas off-limit for breakfast time and hid the bananas. It threw him for a loop when he looked at the empty bowl, asking what is cereal?
Success came quickly, less than a half hour after breakfast, elimination time! I wanted to tie a balloon on the light post but of course, he was unimpressed and calmly went about his day.