What to do when you run out of water
Distill your own water
So you have no potable water, no filter, and the big thirst is starting to kick in. Drinking untreated water may give rise to more problems than you already have, but you can distill your own pure water with only a pot, a cup and a clear plastic bag (or maybe a part of your groundsheet). The objective is to encourage water to evaporate from the pot, condense on the plastic and then collect in the cup.
Find a sunny spot where your still won’t be disturbed. Place the cup in the centre of the pot and fill the bottom of the pot with untreated water, but not so much that the cup floats.
Cover pot with plastic
Cover the pot with the clear plastic. Use a stone to weigh down the centre of the plastic so an inverted cone forms, pointing down toward the cup.
Cup collects purified water
As the pot warms in the sun the untreated water will evaporate, condense on the plastic, roll down to the centre and drip into the cup. Given sunny conditions, you’ll produce enough water to keep yourself alive while you search for a twist of lemon to liven things up.