Sudden feelings of hunger and weakness can happen for several reasons. Some are temporary and harmless causes, others needing attention. In this case person feels suddenly emptiness in stomach and feels like eating something. Most of the time they crave for sweet or fried.
Common
Blood sugar (hypoglycemia) can cause sudden hunger, shakiness, weakness, sweating, dizziness, irritability, blurred vision
Long gaps between meals – if you skip breakfast or lunch, your body demands quick energy, causing hunger plus weakness
Mild dehydration can make you feel fatigued, dizzy, and hunger as thirst and hunger signals are similar
In stress or anxiety, adrenaline and cortisol spikes can cause sudden hunger or energy dips
Lack of sleep disrupts hormones (ghrelin & leptin) that regulate hunger and energy
Underlying conditions can be diabetes or pre-diabetes, thyroid imbalance, anemia adrenal fatigue or hormonal issues
Home remedies
Eat a balanced small snack with complex carbs, banana, sweet fruits, protein handful of nuts
Drink a glass of water when suddenly hungry
Sit or rest for a few minutes, avoid sudden exertion if feeling weak
Management of diabetes medicine should be proper
Check blood pressure
Eat small, balanced meals every three-four hours
Drink eight to 10 glasses a day
Get seven to eight hours of proper sleep
Manage stress through deep breathing, yoga, and meditation
Sujok Therapy

Apply yellow colour on highlighted area (see figure) and press for five to 10 minutes on same area.
If this problem persists or happens often, consult with your doctor.
(Rajshree Vora is an obesity consultant, dietitian and nutritionist, Sujok therapist, counsellor, and yoga therapist. You can write to her at enquiry@rajshreeyoga.com)