Espresso is a delicious and potent hot drink that many people drink because they like the rich taste better than regular coffee and it wakes them the hell up! In both respects, regular coffee doesn’t hit the spot.
So when your in the local coffee shop why do you see Espresso drinkers with a bottle of water as well?
Espresso is only a small shot of liquid (40ml for a single and 80ml for a double) so a cup won’t be sufficient for hydration hence the bottle of water.
Also, a sip of water BEFORE the Espresso will cleanse the palate making that lovely Espresso taste even better.