You ate more salt and carbs than usual-our body soaks up excess water and holds onto it so when you step on the scale you weigh more than usual. It’s not fat. Just excess water. Aka why we gain weight after eating out since restaurants always pack excess salt and oils into their food
You Ate Later Than Usual- This is literally just you eating later at night so when you weigh-in you have more food in your stomach so you weigh more than usual. Again, it's not fat - just stomach content.
You Weighed Yourself Earlier Than Usual- Which also means you had less time to digest the food you ate the night before so, again, you weigh more simply because of more food in your stomach.
You haven't gone the bathroom
You're Stressed- which causes an increase in cortisol and when you're stressed your body holds onto water weight which can make you bloated and heavier on the scale.
It's Your Menstrual Cycle- the fluctuations in hormones causes your body to bloat and hold onto extra water
You Lifted Heavy Yesterday- when your muscles are repairing they "soak up" water and glycogen to recover so they basically act like a sponge. And, as you know, a soaked sponge weighs much more than a dry sponge.