Synonyms for Vomit?

Vomitus

Matter from the stomach that has come up into and may be ejected beyond the mouth, due to the act of vomiting. 

It's not unheard of to nounify a verb so you might be able to use:

Puke: He was found lifeless, lying in a pool of his own puke.

Upchuck: The volume of upchuck was astounding...who could possibly have so much food and liquid in their stomach at one time?

And kinda related...bile. The liquid, non-food specific stomach acid that is sometimes ejected after a person has no more food in their stomach but the spasms continue to push out the contents of the stomach.

Per MW-Online's definition of vomit:

Synonyms

barf, gag, heave, hurl, vomit, retch, spew, spit up, throw up, upchuck...of these, the following can be used in a nounified version: barf, spit up, throw up, (and as mentioned above, upchuck)

As you noted on comments that your context was a story set in England, I’d suggest the noun ‘sick’.

Defined in the OED as

‘vomited matter’

it is a common British-English usage. The examples from the OED however only go back to the late 1950s so it may not be historically accurate for your 19th century setting.

The OED also includes ‘Spewing n.’ as

‘Matter spewed out or vomited; spew.’

with examples from 1380 to 1880. Be aware though that the only example they give later than 1553 is from a glossary of words from County Antrim and County Down in the north of Ireland:

Spuans, what is vomited

The 1811 Dictionary of the Vulgar Tongue ‘A DICTIONARY OF BUCKISH SLANG, UNIVERSITY WIT, AND PICKPOCKET ELOQUENCE’ has a number of colourful phrases for the act of spewing:

To cast up one's accounts

To cascade

To shoot the cat:- to vomit from drunkenness

To flash the hash

To flay (or to flea) the fox

To pump ship

But seems to lack any word other than ‘vomit’ for the ejected contents. The preponderance of ‘x the y’ phrase alternatives in an historical source but not stand alone nouns suggests that its unlikely that there is a swath of nouns waiting to be found.

Though not a term you'd hear outside the medical community, "regurgitated gastric contents" refers to what is thrown up from the stomach of any animal, including human beings.

• Esomeprazole and Discoloration of Regurgitated Gastric Contents in Infants 1
• Patients recovering from anaesthesia are normally nursed on the side so that regurgitated gastric contents do not pool in the posterior pharynx but are cleared with the aid of gravity. 2
• Anaesthesia and sedation depress or block the functioning of protective upper airway reflexes, making pulmonary aspiration of vomited or regurgitated gastric contents likely. 3

If you write about the "post-mortem" of a character, the medical examiner might use that term.