Here are his details from the CWGC.
Name: TEARLE Initials: S    Nationality: United Kingdom
Rank: Private Regiment/Service:
Army Service Corps Unit Text: 17th Field Bakery
Age: 26 Date of Death: 13/08/1917    Service No: S4/090768
Additional information: Son of William Tearle, of 2A, Portland Rd., Luton.
Casualty Type: Commonwealth War Dead    Grave/Memorial Reference: A. 61.
Cemetery: ALEXANDRIA (HADRA) WAR MEMORIAL CEMETERY

This cemetery is very close to the University of Alexandria. Sidney enlisted for the RASC in Rothwell, Northants, not far from Hinkley, where he was living at the time, but I know nothing of the circumstances of his death. CWGC says that most of the burials were of casualties who died in the Alexandria hospitals from action in Egypt and Palestine. I found that two old boys of the Edward Alleyn Club died in the same month and are buried in the same cemetery as Sidney, so I wondered what was happening in Egypt at the time. According to the CWGC, two troopships were torpedoed in Alexandria Harbour in Dec of 1917, so clearly the action was ongoing.

Wikipedia summed it up thus:
The Sinai and Palestine Campaign during the Middle Eastern Theatre of World War I was a series of battles which took place on the Sinai Peninsula, Palestine, and Syria between January 28, 1915 and October 28, 1918. British, Indian, Australian and New Zealand forces opposed the German and Turkish forces.

This area was known as the Middle Eastern Theatre of war, and Sidney has followed John Henry Tearle 1887 of Hatfield into it – not necessarily knowingly. But it is probable, that, like John Henry, Sidney fought alongside the ANZACS. When attempting to find some history of the 17th Field Bakery, there is simply nothing at all. The medals card below says that Sidney was in the Egypt theatre of war, but this included the Dardanelles, so it was a huge area, whatever the actual Theatre may have been called. Without a detailed dairy account of the activities of the 17th Field Bakery, we won’t know where Sidney was when he was killed or wounded.

The Long Long Trail, a very authoritative source for WW1, in discussing the ASC (the R for royal was added in 1918) had only this to say about the Field Kitchens:

The Supply section, Field Bakeries and Butcheries.
“The ASC provided an important service in the production of bread and meat for the troops in the field. Details to be added shortly.”

If Sidney was wounded, he would have been transported to one of the Alexandria hospitals. If killed, and buried immediately, the site of his body would have been noted and after hostilities ended, he would have been moved to the Alexandria CWGC cemetery. Since this kind of movement of the bodies of casualties was very local, we can assume at the very least that Sidney was killed in Egypt. One thing we do know is that the 17th Division was in Egypt on that day, but I do not know if that actually tells us much.

You can see from the above medals card, that Sidney has been awarded the the 1914-15 Star, the British Medal and the Victory Medal.

Sidney’s parents were William 1869 of Eaton Bray and Ellen nee Rollings. His g-parents were William 1830 of Eaton Bray and Ann nee Rogers. This means he is descended from Thomas 1763 and Mary nee Gurney and that places him squarely on the branch of John 1741.