**Core Concept**
Spontaneous hypoglycemia in non-diabetic individuals occurs due to an imbalance in glucose production and utilization, often resulting from an excessive insulin effect. This can be caused by various factors, including certain medications, hormonal imbalances, or tumors.

**Why the Correct Answer is Right**
The most common cause of spontaneous hypoglycemia in non-diabetic individuals is excessive insulin secretion, often due to a pancreatic insulinoma. Insulinomas are benign tumors of the pancreas that produce excess insulin, leading to hypoglycemia. The insulinoma secretes insulin in response to normal blood glucose levels, causing an excessive insulin effect and resulting in hypoglycemia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Alcohol withdrawal can cause hypoglycemia due to impaired gluconeogenesis and glycogenolysis, but it is not the most common cause in non-diabetic individuals.
* **Option B:** Hypoglycemia can occur in non-diabetic individuals with liver disease, but it is not the most common cause.
* **Option C:** Certain medications, such as sulfonylureas and meglitinides, can cause hypoglycemia, but they are not the most common cause of spontaneous hypoglycemia in non-diabetic individuals.

**Clinical Pearl / High-Yield Fact**
The Whipple's triad is a classic clinical correlation for diagnosing insulinoma: 1) symptoms of hypoglycemia, 2) low blood glucose levels, and 3) relief of symptoms with glucose administration.

**Correct Answer: C. Insulinoma. Insulinoma.**