Do not eat nor drink on Yom Kippur
“Whatever soul that is not afflicted on that very day shall be cut off” Vayikra 23: 29
Eating on Yom Kippur even less than the quantity the size of an egg of food fit for human consumption deserves spiritual severance.
If by accident, he has the obligation to bring a sin offering.
All foods are added together to give this minimum measure.
If one drinks enough to full the cheek of liquid fit for human consumption, this being the quantity less than a Rivis/ 86ml for the average person is liable for spiritual severance.
All liquids are added together to make up this minimum quantity.
Smaller quantities than the above are forbidden by then Torah but does not bring spiritual severance.
But the sinner should be lashed for disobedience.
According to the Scribes the following are also forbidden on Yom Kippur
Washing, applying oil to the skin, wearing leather shoes and sexual intimacy.
Violation deserves the punishment of lashes for disobedience.
This applies in all places at all times for men and women.