At festival time ( every weekend when I was younger no matter what was going on) all liquid refreshment already comes in a handy container, why would you lug another one around ? Unless it is an already full one to replace the one you are about to finish!
Most of the tat in the articlebelongs at a Pageant of Motoring or similar event, not in a (muddy) field at a music festival; only carrywhat is vitally important, anything else you can take if the bird is willing to carry it.
If you really want hot food without queuing buy the military MREs http://www.hotpackmeals.co.uk/ like these you can carry half a dozen easily in a back pack.
If you don't have a little water to start the exothermic heating reaction, beer works!