I have a U.K. limited company of which I am the sole director and employee. I work from home most days, but I occasionally work at a local coffee shop when I need to get out of the house.
Can I claim the cost of the coffee as a business expense?
Here are the general guidelines on what you should report and pay - but the overall rule is that if it's not a business-related cost then you can't claim it.
In your example, a client meeting may warrant a claim for 'entertaining clients' which could be claimed as a business cost - but buying yourself a coffee to get out of the house isn't a business cost.
It might be the case that the coffee shop would throw you out after some time, and buying say one coffee per hour is needed to use their premises. In that case it would be a business expense, but good luck explaining that to HMRC.
You can always declare it as an expense, and they can reject it.