、。
I recommend telling it to them straight — not beating around the bush.
Literal
Back-tooth [in-に] thing [subject-が] caught-like way-of-speaking [object-を] not-doing, straight-up straight-pitch [with-で] say-for-them thing [object-を] [polite-お]recommend do.
An advice-giving sentence with two great idioms. 奥歯に物の挟まった言い方 ('a way of speaking with something caught in the back teeth') is a ことわざ-derived expression for 'talking in a roundabout way,' 'beating around the bush,' 'not saying something clearly' — as though something is physically preventing plain speech. ズバリ is an adverb meaning 'straight out,' 'frankly,' 'hitting the mark dead-center.' 直球 ('straight-pitch') is baseball terminology used figuratively for 'direct, no-spin communication.' Together ズバリ直球で言う = 'tell it straight.' The polite お勧めする uses the humble お + verbal-noun + する keigo pattern.