I have heard folk wisdom to the effect that a can of Coke a day results a pound of weight gain per month. According to this (somewhat dubious) article, 20oz of soda per day results a pound of weight gain per week!

https://abc7news.com/soda-weight-study-on-how-adds-pounds-ga...

A glass of soda with every meal, maybe more than that. Either way a can of Coke is over 100 calories that don't make you feel full.

I think people react differently and metabolism matters. I find 100 calories is nothing, and you burn that quickly just being alive.

An extra 400 calories a day isn’t nothing.