A hat trick in soccer is scoring three goals in one game. A German hat trick is scoring three consecutive goals in the same half, a much more difficult task.
On a weekend vacation break, having sex with three different (fresh meat) partners is a hat trick. Three partners in a 24 hour period is a German hat trick.
A Swiss hat trick is similar to a German hat trick but quirkier. The difference is no washing during the 24 hour period.
A Swiss hat trick is having intercourse with three different sexual partners within a 24 hour period with zero intimate washing.
You must be a true pulling machine to complete the Swiss hat trick. Ron completed it in Skegness after a couple of previous Swiss braces.