I glanced over the actual study yesterday. Iirc, there was a control group of 65 who were studied on top of the other 50 who received the lump sum of cash. Both groups spent roughly similar amounts of stimulants such as alcohol and other drugs, despite the group receiving financial help obviously having access to more money. I think it makes more sense to think of the homeless’ spending on stimulants as just another need they have developed due to different circumstances on their lives. Would their finances be easier to manage if they didn’t have that spending? Sure, but very, very few people are going to be capable of overcoming an addiction on the short term when they structurally live under shit circumstances. Help them reach a minimum standard of living, then it’ll be easier for them to successfully go through therapy.
TL;DR: Just give homeless people money, they tend to understand their own circumstances well enough to know how they should spend it.