Assign a dealer.
The dealer will deal two cards to each player face up. If you receive an ace you may call it high or low. E.g. If you call it low it will be below the 2 card, If high it will be greater than the king. Have a look around at the other cards dealt; it may help your decision.
Once everyone has two cards the dealer will ask for their bets. You may bet up to five drinks. Your bet will depend upon the probability of the next card being dealt being in between the two cards you already have.
E.g. If your current cards are 5 and a jack then you have the 6, 7, 8, 9 and 10 in between. The odds for the next card to be dealt to you are ok so you would bet 2 or 3 drinks (mouthfuls).
If you had an ace low and a king you’d have the best odds that the next card dealt will be in between these two cards, so you might like to bet 5 drinks (mouthfuls). Or if you have a 5 and a 6 then there are no cards in between these, so throw them in.
The next card is dealt. If this card is in between your current cards then you get to give anyone playing the drinks that you had bet. If the card is not in between your current cards then you must drink the amount that you bet. If the card is the same as on of your current cards then you must skull your remaining drink. This is known as being “hit on the head”
Then it’s the next person go.
The game will keep going until you get bored of it.