Most hospitals have a rule about any food or drink being provided to a patient without the consent of the medical staff for a very good reason.

Some may be as follows:

Possible testing that requires fasting.
The need to monitor intake and output of fluid levels.
Possibly special diet restrictions not already in place.

The list could go on and on. In order to properly treat a patient in the hospital, the medical staff needs to be fully aware of everything that is going into a patient's system, be that food, drink, or medications. Many things could be contrary to the care of the patient.

In some cases, things of which the hospital is unaware, could pose potential danger to the patient. The policies of the hospital are not usually arbitrary, while some may seem to be so.

When one of my family members were hospitalized, I asked if it would be OK if I brought coffee from home for the patient. ONLY, after I had "permission" did I bring the coffee.

Just my take on the food topic.