I knew a self employed person who rented a single office in an office building. They used it to get into the "work" mindset. When working in their home they often found it hard to get into a "work" mindset. Getting dressed and going to an office allowed them to get into a "work" headspace.
If you buy 1-2 cups a day, call it $10-15 a day. 20 work days a month means 200-300 spent at Starbucks is a lot cheaper than any commercial rental office lease and you get 20-40 cups of "premium" coffee and a place to work.