Dextrose. You can't buy it in grocery stores, but it is available online. Don't pay more than $2/lb. It is sold most cheaply labeled "corn sugar", marketed mainly to home beer brewers. There is only one actual supplier in the US, who ships 50 lb bags. Others break it up and sell 10, 5, and 2 lb bags. Some relabel it "dextrose" or "glucose" and jack up the price. I get mine 10 lb at a time from "Homebrew". Regular sug…
Note this is a shortage currently on dextrose because of all the hard seltzers appearing in the market so quickly and using it all up, so it will probably go up as these keep growing.