Mine is that I pour the milk before the cereal. people are always extremely confused by that.
i had one of those apple corer things you press down to cut an apple into slices and leave behind the core in a cylinder.
used it one day at work and started feeling more and more nauseated and dizzy right after eating the apple slices to the point i had to leave work and go home.
i googled it later and discovered apple seeds contain a small amount of cyanide. i guess normally if you don’t chew them they pass through just fine no problem. but that apple corer thing had sliced through several seeds.
i’ve chewed a seed or two before without issues so maybe i got some mutant apple or something but fyi about the cyanide thing!