I don't know about cheap but I bought ours online from their website. I bought the ticket with food. It was $10 more than their discounted one day ticket. You can eat as much as you want from most of their counter service places. Each time through the line you can have an entree, side, drink and dessert but you don't have to take all of that. We got lots of bottled water. That just worked for us. Saved us having to budget for food or try packing drinks etc for the car.
We were also there in June. It was super hot so the drinks and fruit were great