When Habīb Ahmad Mashūr al-Haddād went to Africa to give da'wah, he opened a very small shop and only chose to sell a few items within it which included coffee, tea and sugar. You have to read this because this is true da'wah!
When the local children would come close to the shop, he'd give every single one of them sweets until all the kids of the community fell in love with him and began to oft-praise him and tell their parents about him. When the parents would then come out to meet him and purchase sugar from him, he'd speak to them about Islām and they'd immediately say, 'Lā ilāha ilā Allāh!'
When people would come to buy tea, he'd give them an extra coffee to take back home with them. When people would come to buy coffee, he'd give them extra tea to take back home with them. Eventually, he became extremely known and people began to come often and socialise with him. Whilst in this state of harmony and love, he didn't speak to them about the religion of truth except they'd say, 'Lā ilāha ilā Allāh!'