The Messenger of Allah ﷺ used to fast while travelling and also break his fast, and he would pray two rakats which he never omitted. He would say that he did not add more than that, meaning in the obligatory prayer.
حدثنا روح حدثنا سعيد عن عبد السلام عن حماد عن إبراهيم عن علقمة
أن رسول الله ﷺ كان يصوم في السفر ويفطر ويصلي ركعتين لا يدعهما يقول لا يزيد عليهما يعني الفريضة
Its isnad is daif. Saeed is Ibn Abu Aruba. Hammad is Ibn Abu Sulayman, the jurist of Kufah. As for Abdul-Salam, the Hafiz said in Tahzib 6:325-326, "Abdul-Salam, from Hammad bin Abu Sulayman, and Saeed bin Abu Aruba narrated from him. He is Abdul-Salam bin Abu Al-Junub." Ibn Adi deemed him trustworthy, but even if he were daif, Ibn Abu Al-Junub, with the jim vowelled as a fatha, is extremely daif. Ibn Madini said, "His hadith is objectionable." Abu Hatim said, "A discarded shaykh." The Hafiz relayed in Tahzib 6:315-316 from Ibn Hibban that he said, "He narrates from trustworthy narrators things that do not resemble the hadith of reliable narrators." The Hafiz said, "Then he was careless and mentioned him among the trustworthy narrators without identifying him further."The hadith is found in Majma al-Zawaid 3:158-159, where it says, "Ahmad, Abu Yaala, and Bazzar narrated it similarly, and the men of Ahmad's version are the men of the Sahih." That is what it says! But I have made every effort to find, in the biography of everyone named Abdul-Salam, one who belongs among the men of the Sahih from this generation, and I found none. So I do not know the basis for what was said in Zawaid.