Borei Nefashos During A Meal

The Mishna Berura writes (174:25) that if before washing for a seuda a person takes a drink of something he does not intend on drinking during the meal, he must make a borei nefashos before washing for the seuda.  Furthermore, even if he has washed already, he must still make a borei nefashos during the seuda.  The reason for this is that drinking before a seuda has no connection to the seuda itself and therefore the birchas hamazon after the seuda will not cover this drink.
However, the Mishna Berura writes that just like with wine, if a person drinks whiskey before a seuda he need not make a borei nefashos since the whiskey is connected to the seuda by the fact that drinking things like whiskey and wine whets one's appetite for a seuda.
 
Therefore, if one arrives early at a restaurant and has a drink (other than wine and whiskey) before washing, he should first make a borei nefashos and then wash.  If he washed before making a borei nefashos, he is still required to make a borei nefashos during the meal.

From Revach.net