What characterizes the interpolations in this chapter of 29 verses is the tasteless 'Omnipresence of the Supreme in Brahmins, cows, elephants, dogs and dog eaters' of v18, which could be but an interpolation as it ill-behoves Krishna's eloquence and his sophistication of expression seen throughout the genuine text.
Moreover, V27-v28 that deal with yogic practices, and V29, which asserts the Supreme as the beneficiary of sacrificial rituals, are but interpolation for reasons that bear no repetition.
In response to Arjuna's plea at the very outset, Krishna delves into the renunciation of action.
Ch5, V1
Pray be clear, as Thee aver
Act 'n give up in selfsame breath.
sannyāsaṁ karmaṇāṁ kṛiṣhṇa punar yogaṁ cha śhansasi
yach chhreya etayor ekaṁ tan me brūhi su-niśhchitam
Then, Krishna sets the tone for the self-help with the opening statement thus:
Ch5, V2
Give up all 'n thou be freed
So's the case with selfless work
But know latter scores much better.
sannyāsaḥ karma-yogaśh cha niḥśhreyasa-karāvubhau
tayos tu karma-sannyāsāt karma-yogo viśhiṣhyate
Continuing in the same vein, Krishna affirms that –
Ch5, V17
In clear conscience 'n fairness
Gives man freedom faith in Him.
tad-buddhayas tad-ātmānas tan-niṣhṭhās tat-parāyaṇāḥ
gachchhantyapunar-āvṛittiṁ jñāna-nirdhūta-kalmaṣhāḥ
Next appears the silly and tasteless description of the Omnipresence of the Supreme in Brahmans, cows, elephants, dogs, and dog eaters! Wonder if this is not an idiotic interpolation, then what it is only the blind votaries of the Gita 'as it is' can explain
V18
vidyā-vinaya-sampanne brāhmaṇe gavi hastini
śhuni chaiva śhva-pāke cha paṇḍitāḥ sama-darśhinaḥ
The truly learned, with the eyes of divine knowledge, see with equal vision a Brahmin, a cow, an elephant, a dog, and a dog-eater.
In contrast, the succeeding verse is the true successor of the former (V17).
Ch5, V19
Keeps who equity ever in thought
Faultless being attains he Brahman.
ihaiva tair jitaḥ sargo yeṣhāṁ sāmye sthitaṁ manaḥ
nirdoṣhaṁ hi samaṁ brahma tasmād brahmaṇi te sthitāḥ
Now, over to the other interpolations -
V27
sparśhān kṛitvā bahir bāhyānśh chakṣhuśh chaivāntare bhruvoḥ
prāṇāpānau samau kṛitvā nāsābhyantara-chāriṇau
Keeping external sense objects outside, and eyes in the center of the eyebrows, and also equalizing the incoming and outgoing flow of breath inside the nostrils;
V28
yatendriya-mano-buddhir munir mokṣha-parāyaṇaḥ
vigatechchhā-bhaya-krodho yaḥ sadā mukta eva saḥ
That person who has restrained his senses, mind and intellect, and whose ultimate goal is liberation, who is devoid of desire, fear and anger; that person is also a monk, he is ever liberated.
The v27 that deals with yogic practices and v28 for its ascetic association with it would not fit even in the Gita's spiritual space and thus are but interpolations for reasons that bear no repetition.
V29
bhoktāraṁ yajña-tapasāṁ sarva-loka-maheśhvaram
suhṛidaṁ sarva-bhūtānāṁ jñātvā māṁ śhāntim ṛichchhati
Having realized Me as the enjoyer of all sacrifices and austerities, the Supreme Lord of all the worlds and the selfless Friend of all living beings, My devotee attains peace.
This Supreme as the beneficiary of the sacrificial rituals is but an interpolative hat, and thus these four verses are nothing but inane interpolations.