[3] At the young age of 29, Sinding became head coach of Brøndby's senior team in 1970, which competed in the local divisions under the Zealand FA (SBU).
The first team's final position in the league standings – 10th place in the Sjællandsserien (Zealand Series) – in the 1969 season had been deemed unsatisfactory, and the collaboration with the then head coach Ib Jensen was discontinued and a major overhaul of the first-team squad was made.
This achievement marked the club's second promotion since its foundation where it had been incepted in the Serie 1, the sixth tier of the Danish football league system.
In the following season, however, the club's board chose to appoint Mogens Johansen as new head coach and shortly afterwards, former professional player Finn Laudrup took over as player-coach for the first team.
There, he led the team from the Denmark Series to the third highest tier (3rd Division East under the former league structure) in 1974, which was the first time this occurred in the club's history.
The team had at that point lost six games in a row and bottom of the 1st Division, after which Bøje took over as head coach for the remaining 15 matches of the season and managed to heed the club from relegation, which was secured in the penultimate matchday against Slagelse B&I.
[8][2] Subsequently, in 1979, he became head coach of Hvidovre IF, whom he led to the 1979–80 final of the Danish Cup, which the team won after a 5–3 win over Lyngby Boldklub in Københavns Idrætspark.
[13]After a short period as head coach of Glostrup IC who competed in the 2nd Division (second-tier), he returned to Hvidovre in the position of manager responsible for tactics, team selection, handling contract negotiations, outreach work and collaboration with the youth department around talent work, whereas Hvidovre's former coach Kurt Stendahl continued as responsible for day-to-day training.
Prior to the 1988 season, Sinding moved to newly promoted 2nd Division (second-tier) club Fremad Amager on a three-year contract.
Four months before his contract expired, the board decided to dismiss Sinding with immediate notice on 18 August 1990, which was justified with "a lack of tactical abilities" – despite the team going through an undefeated stretch of eleven matches.
[18][19] After the 1990 season, the team relegated to the Danish 2nd Division (third-tier),[fn 1] and his replacement as head coach, who had already been introduced two months before Sinding's dismissal, was former Fremad player Tonni Nielsen.
He replaced the outgoing Benny Jensen, who had resigned during the summer break, as he had felt that he could no longer implement his ideas, and had, as a result, moved to Vanløse IF instead.
[33] Alongside his football career, Sinding, who became self-employed in 1980 after 12 years at offshore supplier Semco, has been director and owner of a private installation company, W. Johansen ApS.