When The Bread-Winner Goes To The Back of The Line
The Rema (166:1) writes that waiting a long period of time between making an al netilas yadayim and hamotzei on bread is a hefsek just as is talking between washing and making a hamotzei. The Rema writes that waiting more than the time it takes to walk 22 amos (the Piskei Teshuvos writes that this varies according to the poskim between 16-30 seconds) is considered a hefsek.
Based on this Rema, people should be careful to have their bread (sandwich) ready to make a hamotzei before washing so as not to delay too long and create a hefsek between washing and hamotzei. However, it should be noted that if there was a hefsek for a longer period of time, so long as one didn’t have hesech ha’das one need not wash over again.
This halacha comes up often on Shabbos when the head of the household makes the hamotzei for everyone at the table. The Mishna Brura explains (165:6) that to prevent there being a long period of time between the al netilas yadayim and hamotzei, the head of the household should wash last so that his al netilas yadayim is closest in time to his hamotzei.