Complex sentence: A fun variation for turning sequence into drinking game for adults is for each player to pick one (or two) number or face cards and each time that number is discarded the player who chose it has to drink.
Split into simpler sentences: A fun variation for turning sequence into a drinking game for adults is for each player to pick one (or two) number or face cards. Each time any of the chosen cards is discarded, by any player, the player who chose it has to drink.