I don't use sky go however I had a quick look and it seems that on a PC you access it with a web browser.
The user credentials will be stored in Cookies.
Absent a means provided by the web site -
You could delete all the cookies - you would lose all stored usernames/passwords and settings for all sites.
Delete cookies selectively - you may find it tough to ferret out all the required cookies.
Use a completely different browser. Cookies are not shared between browsers.
EASIEST I would think - I do this every day.
Use a private/incognito window of your chosen browser. Many broowsers have this facility. Each time you close ALL such windows all cookies are erased. You don't need to close the whole browser.
With Firefox use a separate Profile - I found this fiddly but manageable. Can't remember details. Each profile has it's own set of cookies.