We all know that in a perfect world, one would have a sink with a nice big washing cup for Netilas Yadayim. However, what does one do when, for example, one does not have a cup? What if one does not have a sink, but only a bottle of water? What if someone drank directly from that bottle?
The Aruch haShulchan (163) sums it up nicely:
Chazal permitted Terumah eaters to eat without washing by merely covering their hands (because they were zerizim and would be careful to not touch the terumah). They did not permit this for people who ate their food in taharah.
The Rambam limits the restriction to those who were careful about taharah, but for us regular food eaters, we could cover our hands, too.
Most Rishonim argue and limit hand-covering to where you cannot find water up to a mil out of your way or 4 mil on your way. The Magen Avraham allows you to rely on the Rambam if you're not sure if their is water within that time frame.
Bottles are fine for netilas yadayim if it has a steady stream.
Dinking doesn't pasul it acc. to Aruch haShulchan 160:10
If one has a sink but no cup, he can turn on the faucet over one hand, shut the faucet, turn it on again and wash the other hand, and so on. This is permissible as the washing is still done with "Koach Yad." I have seen multiple Rabbis do this, and heard it explicitly from a former rabbinical student.