Sneek is definitely worth staying longer than 1 day and an overnight stay is booked! You can stay in Sneek in various ways. Multiple hotels, guest houses and 'bed and breakfast' addresses will be happy to receive you.
Are you with a group? You can also go to Sneek for this, what do you think of Het Boothuis or Het Toppunt, on the open waterway. So you can sail off in the morning after breakfast with your sailing boat to the Sneekermeer or enjoy the boats from your deck chair by the jetty.