And yes, team colored decorations and themed partyware for this occasion are a must - for both teams involved. A 6' deli sandwich is a great way to keep even the pickiest of eaters satisfied. This is a fun way to keep everyone's interest in the game.
Half time is the perfect time for serving the food and re-filling beverages.
Set up a covered table with the food and have plenty of plates, cups, napkins, and utensils for everyone. And since half-time is a break for everyone, loosen up the crowd with some sports trivia. Make up questions of all playing levels and give out prizes. This is also the perfect opportunity to bring out the camcorder if you have one or even disposable cameras. Party pictures and videos of un-noticed moments are always fun to look out later down the road.