Depends what material your top is made of. On the Suzuki that had a vinyl roof I just used tons of Armor All to keep it supple.
On the Abarth that the top is made of a more contemporary elastic fiber I just wash it gently with a medium brush and some regular Meguiar auto wash detergent, nothing too harsh.
The most pain is when the white fluffs start like last week was impossible to keep it clean.
Also bird poop you'll want to wash off as soon as possible.
RaggTopp , un tres bon protecteur pour les toits de décapotable et aussi un tres bon nettoyant safe pour les tissus.
http://www.raggtopp.com/
https://www.eshine.ca/collections/raggtopp-wolfsteins