Crossings from Santiago Cordero (2), Guido Petti and Gonzalo Bertranou helped them to four points, with this their seventh win of 2017.
In reply the Rebels, who won one game this year, had Reece Hodge to thank for 22 of their points while Steve Cummins scored late on.
Despite little but pride to play for, both these outfits were cagey early on and took points when they were on offer via the kicking tee.
The Rebels struck first on three minutes when Pablo Matera was caught offside and Hodge did the rest before doubling that lead soon after.
Sánchez halved the gap on 13 minutes after Lopeti Timani was penalised for a high tackle but that papered over a sluggish start from them. Fortunately for the Jaguares a sloppy home line-out in the Argentine red zone twice let them off the hook as it remained a three-point game.
On 19 minutes however Hodge stepped up again to add three points, this time after Petti was offside, and the Rebels were 9-3 ahead.
Six minutes later, the first try finally arrived and it was worth the wait as a lovely line from full-back Jack Maddocks led to him finding Hodge on his shoulder on the 22 and the centre had an easy run-in. The Wallaby then added the extra two points to take the Rebels 16-3 up.
Credit to the Jaguares though who hit back eight minutes later, with wing Cordero finishing off a blindside scrum move that made it 16-10.
And despite the visitors pushing again late in the half, an earlier Hodge penalty meant that the lead was back up to nine at the interval.