After a tight encounter at Whitley Park, Newcastle's youngsters fell behind in the closing stages of the league clash through Swyer, who raced onto Lewis Orford's lofted pass before firing the ball home.
Three changes were made from the side which claimed a penalty shoot-out victory, following a 2-2 draw, against Bradford City in the Bristol Street Motors Trophy as Alex Murphy, who received an international call-up with Republic of Ireland at under-21 level, was handed a start as well as Trevan Sanusi and Leo Shahar, who both made their debuts for England at under-18 level earlier this month.
Swyer almost sent Newcastle behind in the opening minutes after connecting with Ryan Battrum's cross from the right flank but the forward's first-time strike at goal flew narrowly wide of the left-hand post.
Magpies goalkeeper Aidan Harris, who saved two penalties in a shoot-out victory against Bradford City in the EFL Trophy, produced a key save to prevent Orford from opening the scoring, with the 17-year-old shot-stopper getting down well to push away the Iron skipper's strike inside the box before the loose ball was cleared for a corner.
Jay Turner-Cooke, who spent the first-half of the 2023/24 campaign on loan at Scottish Premiership side St Johnstone, was unable to trouble Finlay Herrick shortly after as the attacking midfielder's free-kick from the edge of the penalty area was comfortably held by the Hammers goalkeeper.
Hammers defender Luizão almost netted an own goal as Johnny Emerson's teasing cross from the left flank took a slight deflection from the Brazilian centre-back before the ball curled inches past the right-hand post.
In the second-half, Ben Parkinson almost broke the deadlock as the Durham-born teenager latched onto Turner-Cooke's pass but could only direct his powerful effort wide of the target.
Sanusi, who made his first-team debut for Eddie Howe's side during a pre-season friendly win against Hull City, almost grabbed his first goal of the 2024/25 campaign at second-string level as the Birmingham-born winger advanced inside from the left flank before the 17-year-old's resulting effort was beaten away by Herrick.
The England Under-18 international went close once again minutes later after dangerously darting past a group of Hammers defenders before his low shot inside the box was saved by Herrick before the West Ham goalkeeper smothered the loose ball.
In the 77th minute, Newcastle fell behind as Swyer netted for the visitors, racing onto Orford's lofted pass and, after holding off the challenge of Magpies skipper Cathal Heffernan, fired the ball beyond Harris.
Newcastle United Under-21s: Aidan Harris, Leo Shahar, Cathal Heffernan, Charlie McArthur, Alex Murphy, Anthony Munda (Alfie Harrison 63), Travis Hernes, Jay Turner-Cooke, Johnny Emerson (Josh Donaldson 71), Trevan Sanusi, Ben Parkinson.
Subs not used: Ciaran Thompson, Adrian Janusz, Ellis Stanton.
