Written and first recorded by Tommy James & the Shondells (1968).
Hit version by The Clique (US #22 1969).
From the wiki: “‘Sugar on Sunday’ was written by Tommy James and Mike Vale, and was first recorded by Tommy James & the Shondells in late 1968 for inclusion on the Crimson & Clover album.
“The Clique was a late 1960s American sunshine pop band from Houston, Texas. They started as the Roustabouts in the Beaumont, Texas area, 90 miles east of Houston, and later the Sandpipers before renaming themselves the Clique in 1967 and settling in Houston. Their first hit was a cover of the 13th Floor Elevators’ ‘Splash 1’, on Cinema Records, produced by Walt Andrus. The song was #1 in Houston for several weeks. Their self-titled album, The Clique (1969), released by White Whale Records, featured the singles ‘I’ll Hold Out My Hand’ and ‘Sugar on Sunday’. The latter single reached #22 on the Billboard Hot 100 in October, 1969.”
The Clique, “Sugar on Sunday” (1969):