Some breweries used to (may still for all I know) sell 4 pint plastic jugs for the take home trade. You bought the jug well before closing, had the barman carefully pull half a gallon into it and then carefully push down the pressure seal in the centre of the cap. This prevented the beer leaking or going flat. I took a pair of these, empty of course, to the Cider House in Newton Abbott and had them filled with rough, just before catching the train back to London. Popped them into my big blue canvas holdall and shoved it on to the luggage rack opposite. Half an hour later I noticed that the blue canvas was looking a bit darker in hue and, slightly damp. Inside the space of 30 minutes, the cider had eaten through the rubber grommets sealing the pressure caps of the jugs. I had to drink a pint or so from each jug to get the cider down to a safe non spillable level. It made changing trains at Reading an interesting experience.