Do the Sunan al-Fitra – such as using a siwak and using a toothbrush and toothpaste – require the intention of sincerity to Allah Almighty, or is it permissible to do them with the intention of being praised by people without being condemned by them?

The Sunan al-Fitra (practices of natural disposition) can be performed with the intention of worship, in which case sincerity of intention to Allah is necessary to attain reward. Or they can be performed for the sake of cleanliness or habit, in which case no reward is given except with intention, because they are acts of worship whose meaning is understood. If they are observed as acts of worship, then sincerity of intention to Allah is obligatory. If they are performed for cleanliness or to consider people's opinions, there is no harm, but there is no reward in them except with intention. And whoever performs the Sunan al-Fitra without intention, his obligation is fulfilled, even if he does not receive the reward.