In The Name of Allaah, The Most Merciful, The Bestower of Mercy
What I know from the people of knowledge are two views;
Some of the scholars say that the prohibition of drinking whilst standing is a Nahyun Tanzee (i.e. a prohibition indicating that the action is disliked but not impermissible). Therefore, the prophet (sallal-laahu-alayhi-wasallam) standing whilst drinking is an indication of the permissibility of the act. Some other scholars say that the Prophet (sallal-laahu-alayhi-wasallam) standing whilst drinking was specified to drinking Zamzam water.
However, the principle utilised by Imaam Shawkaanee with regards to the likes of these narrations is that a statement made by the Prophet (sallal-laahu-alayhi-wasallam) is applicable to the Ummah (i.e. they are to abide by what it indicates of commands, prohibitions etc.) and the Prophet’s action in (this instance) is specified to him (i.e. it is only allowed for him); because his statement (i.e. that one should not stand whilst drinking) is in opposition to his action (i.e. he stood drinking). This is what is available to me from the speech of the scholars and Allaah knows best. [Paraphrased: Source: Asbaab Al-Ijaabah, cassette 2]