To splash out is to spend generously on something special. Splash out on a meal, splash out for once.
It is affectionate rather than critical, since the point is that it is unusual. It takes on before whatever the money went on.
1phrasesplash outTo spend generously on something special.
“They decided to splash out on a proper hotel for the anniversary.”
splash out is a phrase.
Practised in Shopping & Money