I have one domain:
sport-clothing.com and I want to create another shop (different content) with name
Will such similar domains affect SEO of both negatively?
Search engines will consider these two domains as different for SEO (because of the different URL) even if these two websites:
Therefore, if you don't use duplicate content, there is no reason why one domain can affect negatively SEO of the other.
There are lots of websites with similar domains out there so this won't be an issue. You will only run into issues if you use duplicate content on these two sites (which the domains suggest is probable). If you plan on the second site being a clone, or a slightly different version of the first, you will have duplicate content issue which will hurt the second site for sure and possibly hurt the first one as well.