Complex sentence: Rothmans then transferred their association to Williams F1 during the World Championship from 1994 until 1997, after which sponsorship was transferred in 1998 to Winfield, another sister brand.
Split into simpler sentences: Rothmans then transferred their association to Williams F1 during the World Championship from 1994 until 1997. Sponsorship was transferred in 1998 to Winfield, another sister brand.