What is the ruling on using bathtubs in bathrooms by pouring a small amount of milk, honey, and aromatic substances to cleanse the skin?

It is not permissible to place food in unclean places, because food is a blessing that must be respected and not demeaned. This is an act of extravagance, which is dispraised in Islamic law. Islam permits adornment, but within the bounds of moderation and balance. Allah Almighty says: "O Children of Adam, take your adornment at every place of prostration. And eat and drink, but be not excessive. Indeed, He likes not those who commit excess." [Al-A'raf: 31], and His saying: "And do not spend wastefully. Indeed, those who spend wastefully are brothers of the devils" [Al-Isra: 26-27]. Using the materials mentioned in the question in the manner described involves extravagance, wastefulness, and degradation. Even if adornment is a legitimate interest, it is a luxury and can be replaced with other materials, unless its purpose is treatment and this means is designated; in that case, necessity permits the prohibited. A Muslim must remember those who die of hunger and cannot find anything to sustain themselves. Goodness can be delivered to them through charitable organizations.