Exegesis:

ho de Petros kai hoi sun autō ‘now Peter and those with him,’ instead of ‘Peter and John and James’ (v. 28), focussing the attention on Peter and thus preparing the reader for v. 33.

ēsan bebarēmenoi hupnō ‘had (in the mean time) been weighed down with sleep,’ pluperfect tense, indicating a situation which had come into existence during the preceding events. hupnos.

bareō (also 21.34) ‘to burden,’ here, in the passive, metaphorically of being weighed down with sleep (cf. Mt. 26.43).

diagrēgorēsantes ‘after waking up.’ Revised Standard Version has “but they kept awake”, but this is less probable.

eidon tēn doxan autou ‘they saw his glory,’ cf. on v. 29.

tous duo andras tous sunestōtas autō ‘the two men who were standing with him,’ second object of eidon.

Translation:

Those … with him, or, ‘his (two) companions.’

Were heavy with sleep, when referring to actual being asleep, as preferred in Exegesis, “had been overcome by sleep” (An American Translation, similarly several others), ‘were very sleepy and took-a-nap’ (Balinese), ‘overcome by sleepiness (lit. closing of the eyes)’ (Tae’), ‘had fallen asleep because their-eyelids-drooped’ (Toraja-Sa’dan).

But kept awake, preferably, ‘but they awoke,’ ingressive aspect.

His glory, i.e. Jesus’ glory, or, ‘him/Jesus in his glory.’

With him, or, ‘close to him,’ ‘at his side’ (Batak Toba), ‘close by’ (Javanese).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.