Question: What’s the best way to wash one’s hands before eating bread when travelling?
Answer: The Shulchan Aruch (OC 159:7) writes that one must actually pour the water over one’s hands, koach gavra. Just holding one’s hands under a running tap would not suffice (See Mishna Berura 159:60).
R’ Eliezer Waldenberg (Tzitz Eliezer 8:7) writes that if one doesn’t have access to a cup, one can open and close the tap a few times, as bedieved this counts as koach gavra (See Mishna Berura 160: 64). R' Yitzchak Yaakov Weiss (Minchas Yitzchak 4:21) disagrees, as the pipe cannot act as a keli.
R’ Moshe Feinstein (Igros Moshe EH 1:114) writes that one should not wash one’s hands in a toilet room, though R’ Yitzchak Yaakov Weiss (Minchas Yitzchak 1:60) writes that when that is the only water available, one should wash his hands there, though they should come out before drying them. If possible, one should fill up the cup and take it outside the room.
One can dip one’s hands into a body of water that would otherwise be suitable as a mikvah. One may wash with other liquids, if necessary, though without a Bracha. (Shulchan Aruch 160:12)
While disposable cups are not ideal, one can use them if that’s all one has. Likewise, one may use a bottle, providing the water comes out in an uninterrupted flow (Mishna Berura 162:30).
While ideally one should dry his hands on a towel, if necessary, one may use an electric hand dryer (Shut Az Nidberu 8:52; 9:64), though it is preferable to wipe them on one’s trousers or skirt.If there is no water around, one is obligated to go the extra mil to obtain water. (That is to go back 18 minutes, or keep travelling for 4 mil / 72 minutes.) If that isn’t feasible, one can cover one’s hands, e.g. with gloves, before eating.