Hiya, for a fanfic I'm writing I need the proper romanization of a
few words.  One is "Black eats Black", a Chinese expression.  The best I
can do is phonetically write, "Hey Tsz Hey"  as you can see (if you know
Chinese) Tsz doesn't even come close to they way "eat" sounds in Chinese.
The other one I need is "Soy Sauce" I put "Jang Yo" for now, but can
anyone help?  Thanks.

hei(1) chi(1) hei(1)

jiang(4) you(2)

...would be the correct pinyin romanization, but you have to know pinyin 
to read it! I think your use of 'hey' and 'yo' is closer for most English 
readers. Perhaps 'hey chir hey' and 'jiang yo'?

For the benefit of the rest of the list:

chi rhymes with cur, not with key

you sounds like yo, not yew

But without pronouncing the tones (1-4), Chinese speakers won't 
understand at all, since the tones are, if anything, more important than 
the rest of the pronunciation.