What can happen to me if I get caught using a fake id to get into a club?

Any person who changes a driver’s license by either giving a false age on a driving application or identification card or by possessing a driver license or identification card,  on which the date of birth has been altered is guilty of a misdemeanor of the second degree.  One can be punished by 6 months of probation or 60 days in the county jail. If you, however, create a counterfeit driver’s license/id card, or possess someone else’s license, it is a felony in the third degree, punishable up to five years in state prison or 3 years probation.  Needless to say, wait til you are 21!

See https://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0300-0399/0322/Sections/0322.212.html