The Mayim Achronim vessel:
Pouring versus dipping? The Mayim Achronim water must be poured onto the hands, as explained in Halacha 6. Thus, a vessel is commonly used for the pouring, and it does not suffice to simply dip the hands in a sink, or river. See Q&A below for the specific details regarding this vessel.
Pouring into a vessel versus pouring on the floor: One may not pour the water of Mayim Achronim over the ground [i.e. earth] and rather it is to be poured into a vessel. If one does not have a vessel available, one may perform Mayim Achronim onto twigs, and the like, that are on the ground. Likewise, [if a vessel is not available] one may perform Mayim Achronim over any item that is on the ground and separates between the water and the earth. Hence, one may pour the Mayim Achronim onto a tiled floor. Furthermore, one may even pour the water onto earth if it is in an area where people will not pass until it dries up. Accordingly, it is permitted to pour Mayim Achronim under the table [even if the ground is made of earth].
Q&A on the vessel used to pour from
Must one use a vessel to pour the water for Mayim Achronim?
There is no requirement to use a vessel for the washing of Mayim Achronim, so long as the water is coming in a pouring position. [One can thus open the faucet of the sink and wash. Likewise, one may use an invalid vessel, such as a vessel that is cracked. Nonetheless, some write that according to Kabala, it is proper to use a vessel for pouring Mayim Achronim.]
May one pour the Mayim Achronim from a vessel used for eating and drinking [i.e. cup, bowl]?
It is permitted to use eating utensils for pouring Mayim Achronim, and it is not necessary to use a designated or disposable cup and the like. Nonetheless, some are accustomed to beware not to perform Mayim Achronim from leftover drinking water.
May one use a gold or silver cup for Mayim Achronim?
One is not to designate a fancy vessel for Mayim Achronim. One is thus to avoid doing Mayim Achronim using a Kiddush cup.
May one drink the leftover Mayim Achronim water?
Yes. There is no reason or source for avoiding drinking the leftover water that is in the vessel used to pour the Mayim Achronim, and there is no source to claim that such water becomes impure. Thus, one may pour Mayim Achronim from a water bottle and then drink the remaining water in the bottle. Nevertheless, some are accustomed not to pour from drinking water, as stated above.
Q&A on the vessel used to pour into
What type of vessel may one pour the water into?
The vessel used should be cheap and simple. Some write that ideally, one is to beware not to use the vessel for eating and drinking, and hence it should be designated for use of Mayim Achronim. They warn that the water contains much impurity and brings illness if one were to reuse the vessel for food or drink. However, some Poskim rule that one who does not have a designated vessel to pour Mayim Achronim into, or if he is too lazy to get it, may pour the water into an empty meal vessel that is on the table.
May one pour Mayim Achronim into the sink?
From the letter of the law, it is permitted to do so, although it is proper to not to pour the water over any vessel that is in the sink, as explained above. If the sink is empty, one may wash Mayim Achronim directly into it, and then wash out the sink. Nonetheless, initially, it is to be poured into an actual vessel as stated above in Admur.
Must one remove the Mayim Achronim water from the table before Birchas Hamazon?
It is proper to remove the vessel which contains the Mayim Achronim water from the table, prior to Birchas Hamazon. It can be placed anywhere on the side, so long as it is off the table.
What is one to do with the Mayim Achronim water that was poured?
If the water was poured into a vessel [as Halachically required] then it does not contain any impurity and one may discard it wherever one likes. Nonetheless, it is best to initially beware to discard them similar to the water of the morning washing [in an area that no one will come to benefit].
 Admur 181:2; Ketzos Hashulchan 43:3
 Admur ibid; Michaber 181:2; Chulin 105a
The reason: This is due to the evil spirit that resides on the water upon it touching the ground. [Admur ibid; Michaber ibid; Chulin ibid] It is dangerous for one to step on these waters. [Levush 181; Soles Belual 181:2; Kaf Hachaim 181:11]
 Admur ibid; Michaber ibid; Chulin ibid
 P”M 181 A”A in end; Kaf Hachaim 181:13
 The reason: As the evil spirit only resides on an earth floor, and not on an intervening item that rests on the floor. [Admur ibid; M”A 181:2; Chinuch Mitzvah 430; Kaf Hachaim 181:11]
 Admur ibid; M”A 181:2
The reason: Although people occasionally move their tables and hence it can end up that a person will walk over this area, nonetheless by the time this occurs the floor will be dry. [Admur ibid; M”A 181:2]
 Levush 181; Kol Bo 23 in name of Ravaad; Kaf Hachaim 181:10 M”B 181:21; Piskeiy Teshuvos 181:13
Other opinions: Some Poskim rule that the water of Mayim Achronim requires Koch Hadam, and thus must be poured from a vessel. [Shiltei Giborim, brought in Beir Heiytiv 181:8 and Shaar Hatziyon 181:31]
 Shulchan Hatahor 181:4 based on Arizal; Piskeiy Teshuvos 181:13
 Piskeiy Teshuvos 181:13
 Nimukei Orach Chaim 303 washed from a large drinking cup; Piskeiy Teshuvos ibid that there is no source for avoiding doing so
 Seemingly, due to the fact that some Poskim record that washing from leftover drinking water leads to forgetfulness. [Kaf Hachaim Y.D. 116:206; Piskeiy Teshuvos ibid footnote 52]
 Taamei Haminhgaim; Piskeiy Teshuvos 181:13 footnote 18 and 51
 The only water that becomes impure by Mayim Achronim is the water which falls onto the ground. Even the water that remains on the fingers remain pure and we hence do not require drying and allow for one to move them over his lips.
 See Sefarim brought in Piskeiy Teshuvos 181:6
 Amudei Kesef [author of Misgeres Hashulchan] on Shut Min Hashamayim, brought in Piskeiy Teshuvos 181:6, writes as follows: “Majority of the illnesses come as a result of pouring the Mayim Achronim water or morning washing water into a vessel and then using that vessel for food. This applies even if one washes the vessel in between, nevertheless it does not suffice. Therefore one must designate specific vessels for this purpose and not use them for other matters.”
 Ikarei Hadaat 9:17; Kaf Hachaim 181:8
 This follows the understanding in Poskim, including Admur ibid, that the water poured does not contain impurity unless it reaches the earth.
 See Yabia Omer 5:2; Piskeiy Teshuvos 181:6
 Kaf Hachaim [Falagi] 25:3; Kaf Hachaim 181:8; 173:15; Ketzos Hashulchan 43 footnote 10
 Kaf Hachaim 181:12
 Implication of Admur and Poskim ibid