A weekend warrior might be someone who partakes in war games over the weekend. Without knowing the context it is not possible to be definitive.
A social drinker is a person who indulges in drinking with friends, colleagues or clients/customers for the purpose of being social, not because s/he wants to drink a lot.
Depending upon the context, "weekend warrior" sometimes refers to someone who works as a professional during the week (say, a doctor or lawyer) but partakes in recreational drugs on Saturday and Sunday.