Hello There!
First, let me just explain briefly what is an independent variable and a dependent variable.
An independent variable is the variable that changes during an experiment to see if it has an effect on another variable.
A dependent variable is what is being measured in the experiment. It’s also known as outcome or effect.
In this case, the dependent variable is the number of liters of water your drink because that’s what your measuring.
The independent variable is the number of times you drink all the water in your bottle because that changes during the experiment.