Judging by his size, one might think Charles Barkley would eat anything -- and everything -- put in front of him. Not true.

We're told Chuck had a serious problem with the food he was served during his short stint in an Arizona jail. Charles was given sloppy joes, potatoes, pear chunks, zucchini, a bread roll and a slice of margarine.

His reaction -- "Man ... this stuff tastes like sh*t."

Chuck's special tent, separate from the other inmates, did not come with access to the vending machines with junk food/candy. So his lawyers were allowed to bring him some junk food and candy from the outside.

You can lock up the man ... but not his sweet tooth.