spend like a sailor (on (shore) leave)
To spend excessively, extravagantly, or wastefully. Now don't go spending like a sailor on shore leave just because you got a bit of a tax refund from the government. The local council has been spending like sailors on this new tram project, while other existing public transport goes into disrepair. Every time my husband's paycheck comes through, he goes out to the pubs and spends like a sailor on leave!