Can eating sugar give you a headache?

Hypoglycaemic headaches and migraine. Fasting, eating high-sugar foods, dieting too rigorously, and skipping meals can all trigger, or make people more likely to have a headache or migraine. Even delayed or irregular meals can make a difference. This is usually due to people's blood-glucose levels falling too low.
Hypoglycaemia - The Migraine Trust
https://www.migrainetrust.org/about-migraine/trigger-factors/hypoglycaemia/