Is it permissible to pay the fasting expiation in cash for a diabetic who breaks his fast in a restaurant and is not married, and can it be distributed to three or more needy people due to the absence of someone in need of breakfast?

If you are able to fast, then fasting is obligatory upon you, and it is not permissible to break the fast and merely feed the poor. Insulin injections do not break the fast. You must make up for the days you missed.

However, if fasting harms you, or causes you severe hardship, or you need to take medications during the day, then you are permitted to break your fast. If you are unable to make up the fast, then you must feed one poor person for each day. It is not permissible to give the expiatory payment (fidya) in cash; rather, it must be in food. You must search for the poor or delegate someone to deliver the food to them.