Iām trying to cancel my subsription and trial. Guide says go to Settings ā Billing, but there is not such option. There seems to be no Billing page at all. There seems to be no way to cancel subscription at all.
Top right there is a link for info, which leads to Apple AppStore guide how to cancel subscriptions made via AppStore.
The Sketch app itself is good. 
Hello @jmetsaniemi
Thank you for reporting this. To cancel subscriptions that started from the Mac Apple Store, follow these steps:
Go to Sketch, log in as an Owner, and switch to your Workspace in the top-left corner. Make sure your Workspace name is displayed.
At the bottom of the left sidebar, click on Settings > General to open the Settings page.
You will find the Delete Workspace button. Click on it and confirm the deletion in the prompt that appears.
If there are documents stored within the Workspace, make sure to download them locally before deleting your account. Once a Workspace and Sketch account have been deleted, they cannot be recovered.
If you need further assistance with this process you can count with our Accounts Operation team to assist you.
Cheers 