When it comes to spending money recklessly, there are plenty of synonyms for the phrase "throw money at". For instance, one could say "splash the cash" if someone is spending an excessive amount of money without proper reasoning. Another phrase that can be used is "burn a hole in one's pocket" which describes someone who is unable to control their urge to spend. Additionally, "empty one's wallet" can be used for someone who spends all or most of their money on a specific thing. Lastly, "lavish spending" is a term used to describe someone who spends money in an extravagant way, without thinking about the consequences. All of these phrases revolve around excessive spending and are excellent synonyms for the term "throw money at".