This large stitch cardigan from Garn is one example of a quick and easy side to side sweater pattern using two threads on 20mm needles for sizes sm, med, lg, XL, and XXL. Garn provides ample diagrams and tutorial videos, but the sweater is worked all in stockinette stitch, so it's an easy pattern and suitable for all knitting proficiencies.
Coats and Clarks provides an easy crochet cardigan worked sideways on a USk-10.5 hook (6.5mm). The gauge is 11 sts = 4", so the sweater will work up fast and easy for sizes sm, med, and large. Side to side crochet cardigan pattern link is a free pdf download and print out.
Don't miss this popular look-alike free pattern for Elizabeth Zimmermann's BSJ baby surprise sideways garter stitch baby jacket.
More sideways knits and crochet for children: