Hmm, interesting game.

There are some things that you can change in this script.

on * :TEXT:*:?:{
  if ($1 = set) {
    if ($2 = s-word) set %s-word $3

can also be:

 on *:text:set s-word *:#: { set %s-word $3 }

Since there are no restrictions to whom can change the secret word, it's going to be a hard to keep track since it might constantly change.

When someone gets the secret word right, the bot hands him/her a random drink or snack from the .txt file; because the .txt file is so small, you can use variables and tokens to get a random item.
So you can just take out the on load and then change the third text event to:

on * :text:*:#:{
  if %s-word isin $1- {
    var %prizes Cheerwine|Twix|Pepsi|Dr. Pepper|7 Up|Hershey's Chocolate Bar
    msg $chan Hey, $+($nick,$chr(44)) you just said the secret word $+($chr(40),%s-word,$chr(41)), you get a prize!
    .describe $chan hands $nick a(n) $gettok(%prizes,$r(1,$numtok(%prizes,124)),124)
    unset %s-word
  }
}

If you haven't used tokens before, it's pretty easy.
$gettok "gets the token" from %prizes (first parameter), from the Nth token (second parameter), which is separated by $chr(124) (the |, which is the third parameter in $gettok). $r(1,$numtok(%prizes,124)) means a random selection between 1 and the number of tokens separated by $chr(124), in %prizes. Since you already know the # of tokens, which is 6, you can just use $r(1,6) instead.

• I just realized that there was a command that you made, called !prize add. So instead of writing it into a .txt file, you can also /set it into %prizes. But I figure in this case, if you were to add MANY items to the prize bank, then .txt files would work better. If it's a subtle amount like 10, variables are okay.

If you're interested in learning tokens (which can really cut a lot of your script space), you should look it up in the help file for more info. /help Token Identifiers.

If you didn't already know, you can group things with $+ instead of the method you used.

%s-word $+ .

can be rewritten as

$+(%s-word,.)

. Same with

( $+ %s-word $+ )

, which can be rewritten as

$+($chr(40),%s-word,$chr(41))

. Because parentheses are parameters for scripts, you have to use $chr(40) "(" and $chr(41) ")" instead.

If this is going on a bot, then you might want to "silence" the /describe, by putting . (a period) in front of the command.
This same concept works with /msg and /timer

Some suggestions from me:

• A trigger for starting the game.
• Time-outs if nobody can get the word.
  I think it should be more game-based rather than just random guessing. :\ But it's just an idea.