Game prizes without spending money
Offer a choice, a role or a reusable award. Tell the group what the prize is before play.
Choose the next activity
Let the winner choose between activities that already fit the room and time available. Give a bounded choice rather than control over the whole event.
Make a paper award
Write the game and date on a sheet and let the group add a short message. Keep it about the activity rather than judging the person.
Use a travelling trophy
Choose an ordinary object already available, give it a temporary name, and return it after the next event.
Share the recognition
Recognize clear explanations, helpful hosting or a good team name as well as the final score. Decide those categories before the round.