The stuff that they used to bring in was called brandy

TCD MS 10823 folio 25 recto

TCD MS 10823 folio 25 recto

[April-Sept 1918] plenty of lettuce, carrots, beans, peas, vegetable marrows, parsley, beetroot, radishes and mustard and cress, and these helped to counteract the effect of always living on tinned meats besides providing an additional interest in their cultivation.
Many of the officers kept rabbits, which had large families and rabbit pie became a fairly frequent dish. At one time the rabbit hutches were near the wire, but after it had been discovered that one of the hutches  covered the entrance to a tunnel that was to go outside the wire, they were all removed to the centre of the camp by the German authorities.
The electric light in the camp was not turned out until eleven o’clock, so that it always gave one time for a game of bridge after dinner. For many however bridge was not an exciting enough game, and poker and roulette used to be played instead for very high stakes, so that it was <not> at all an uncommon thing for a hundred pounds to be lost or won in a night. <Settling up used to be done by cheques, usually once a month>.
The worst part of Furstenberg was that it was possible to get spirits into the camp by means of the Russian orderlies. The stuff that they used to bring in was called brandy, but it had never seen a grape and was manufactured locally, chiefly I believe from Sulphuric Acid and Fusel Oil. It had a most nauseating taste and I am afraid ruined many a constitution. Besides this there was a canteen where German wines were sold and also Port and Sherry of a kind, so that there was really no need for these spirits to be brought in, but it was impossible to stop it.