Hydration
TL;DR
something.
How much? What counts?
Coffee and tea are not strong enough diuretics to worry about.
Water in food counts.
NHS: 6 to 8 cups or glasses of fluid a day - https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/water-drinks-nutrition/ - https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/the-eatwell-guide/
- likely to meet the 2l unofficial recommendation (8x 250ml glasses)
Less likely to detect dehydration over the age of 60.
Your urine should be a clear pale yellow colour, except maybe in the morning.
Alcohol is not good, what's new.
Water is best.