I believe that most difficulty resulting from fasting is due to how the fast was broken.
The part that most people don't realize is that the systems of the body have been shut down by a fast, especially the digestive system.
At this point it can't handle very much and the "breaking" period is where the systems are gently woken up.
This "waking up" has to be done extremely gradually or it risks being overloaded and short circuited.
Soft fruits like Watermelon are an excellent choice and one should still take it in less and more slowly that on would like.
I don't believe a fast can be broken too slowly or too gently.
Dairy foods of any kind is one of the worst choices for breaking a fast.