Egyptian water isn’t poisonous honestly it isn’t. Lots of Western people drink it in Egypt. It is so heavily chlorinated nothing could survive in it but your stomach is not used to. So better stick to mineral water. Filtered water is getting more common and you maybe offered that as an alternative.
Again these are safe to eat with a few sensible precautions. In a tourist establishment for example these will be washed in filtered or bottled water so perfectly safe. In our restaurant we serve a number of different delicious salads.
Here are some of the food and drink you will find at local restaurants. You can even buy it and cook yourself.
Buffets that have been left for hours and rice! Yes believe it or not rice that has been reheated or allowed to stay tepid for hours is the most common breeding ground for tummy bugs. Small local restaurants that freshly prepare your food are the safest. If you have to wait a long time, this is good. It means they are cooking it not reheating it.