You have probably already seen one of the 161 “Vélo Bleu” bike rental stations in Nice. It costs 1,50€ to subscribe, the first 30 minutes are free of charge, the following 30mins cost 1€ and then each additional hour costs 2€. So, if you rent the bike for 5 hours you have to pay 10,50€ (1,50+1+2+2+2+2€). You can cycle from the Promenade des Anglais in Nice to Cagnes sur Mer and beyond.
Please check on https://nicecotedazur.velobleu.org/nos-stations/ where to find the stations and how to use the self-service (website is in French only, explanations in English are available at each station).