Choosing to Give Up in battle does not remove the Wisdom buff. It seems to be flagged to be removed when the battle comes to a conclusion where either the enemy party or the player(s) involved are actually outright defeated. Ergo, choosing to Give Up is a valid option in a losing fight to retain the buff and not have wasted the use of the candy.
The effects of the candy do stack with a Wisdom buff granted by the environment, e.g., the +20 Wisdom naturally granted inside dungeons (though some might be bugged and not give the bonus).
