Thanks for writing your query.
After reading your post, it seems that your father had a Vasovagal attack.
It can occur due to drop in blood pressure leading to decreased blood flow to the brain and resulting in unconsciousness
When such an attack occurs, the patient should be lied down with foot end raised. This will increase the blood flow to the brain and help in recovering faster.
Also try to maintain his blood pressure by giving him healthy diet.
He should also drink hydrating fluids.
He should be investigated for :-
2. Serum electrolytes.
Clinical examination and investigations will help in planning his medical management.
I hope this is helpful to you.