If you have a donut shop ... a brick and mortar store ... then you cannot claim any home office expenses of any kind since you have a place of business. You don't make/sell the donuts from your home... it is not the place of business. Your choice to set up a space to work from home for your convenience is a non deductible personal expense.
You can take the office in home expenses if you meet the "regularly" and "exclusively" tests.
To deduct expenses related to the business use of part of your home, you must meet specific requirements. Even then, your deduction may be limited.
General Rules
To qualify to claim expenses for business use of your home, you must meet the following tests.
1. Your use of the business part of your home must be:
------a. Exclusive (see below),
------b. Regular,
------c. For your trade or business, AND
2. The business part of your home must be one of the following:
------a. Your principal place of business
------b. A place where you meet or deal with patients, clients, or customers in the normal course of your trade or business, or
------c. A separate structure (not attached to your home) you use in connection with your trade or business.
Review this IRS website for Home Office eligibility - https://www.irs.gov/businesses/small-businesses-self-employed/home-office-deduction
IRS Publication 587 Business Use of Your Home - https://www.irs.gov/pub/irs-pdf/p587.pdf
TurboTax support FAQ for a home office - https://ttlc.intuit.com/questions/1901224-can-i-take-the-home-office-deduction
