Water
Tap water is safe to drink but heavily chlorinated.
Keep well away from stagnant water, muddy banks, etc. (schistosomiasis is a common hazard).
Cairo Tour
As anywhere, pickpockets so obviously keep your phones close. Bring hand-sanitiser and toilet roll!
Bottled water from street sellers is probably tap water!
Keep fairly well covered up boys and girls.
Rabies is a problem so avoid touching stray cats and dogs (and bats and monkeys if you happen to see any flying or jumping about!). Hahaha.