My sister gets food stamps. Food stamps are for food (generally) where as money is for anything. UBI is often held up by proponents as a replacement for all other support. Given them $1k a month cash instead of whatever they get now. But what they get now is trying to solve a problem not solved by UBI, namely that they can't be responsible for themselves (for whatever reason, physically unable, mentally unable, kids, etc...) UBI doesn't fix that problem so the existing programs will still need to exist.
Anyone unable to be responsible can receive their UBI via a cashless welfare card (https://en.wikipedia.org/wiki/Cashless_Welfare_Card) which quarantines where the money can be spent. It deals with issues like problem gamblers and people with substance abuse problems.