The 10 people, a mixture of men and women, were all aged between 17 and 23.
They were each given a fine for non-essential travel and gathering in a social group at an abandoned building (Beach Grove Hall) in Manby.
Lincolnshire Police officers attended the scene at around 9.30pm on Saturday (March 6).
Inspector Sarah Constantine said: “This is a blatant disregard for the current Covid legislation.
“This group not only put themselves at risk of injury but also emergency services staff at risk of injury by entering this site.
“Breaches like this can also have an impact on the NHS.”