I find a day indoors close to the loo and plenty of water helps. Gives the bladder a good stretch which stops it overreacting. Sometimes I down a litre of cranberry juice first, but I am reliably informed by my daughter that cranberry is a waste of time but it probably helps keep a balance of salts.
What I usually do is have my usual (very weak) tea, then keep a glass of water by me which gradually disappears so I refill it. I started doing it to work out how much water I needed to drink after coming out of hospital where you have a jug by your bed. I think it is better than downing x litres because what you need will depend on your activity and the weather etc - you probably only need a jugful extra over the day.
I find the combination of falling oestrogen and instant coffee a bit of a disaster.