A slightly more recognisable way of writing it would be “d’ya eat yet?” But “d’ya eat” becomes elided even further down to “dyeat”, which can be reanalysed as “jeet”. I’m not really sure what the phonotactics are behind “yet” becoming “chet”, but in this sentence…yeah, it just kinda does.

edit: wait no I worked out why “chet”. It’s the /t/ at the end of “jeet”. /tj/ becoming /tʃ/ is very common across English.

edit 2: to be more precise, dy (/dj/) becoming j (/dʒ/) is also yod coalescence. So it’s all about yod coalescence + allision.