Ntillat Yadayim

Question

If you don't have a cup, can you wash your hands under faucet? If the first answer is "no," would it matter if the faucet is the kind you have to hold to keep the water running? If the answer to the previous question is that it is OK, what if the water stays on by your hand breaking the circuit, i.e., it goes off when you take your hand away from the stream?