Daily Halacha: Can You Immerse Dishes or Refrigerate Food on Shabbat?

Can dishes or utensils be immersed (toveled) on Shabbat?

Yes. According to halacha, it is permitted to immerse vessels (do tevilat keilim) on Shabbat, and there is no issue of fixing or preparing them, as long as the immersion is not for the purpose of removing ritual impurity (tum'ah).

The Mishnah that discusses the prohibition of immersing utensils on Shabbat was referring to immersion for purity reasons, like when someone wants to remove ritual impurity. But when it comes to immersing new vessels to make them ready for use, this is allowed on Shabbat.
This ruling appears in Yalkut Yosef.

Can you return food to the refrigerator on Shabbat?

If food was left out of the fridge, and there’s a concern that it might spoil, it is permitted to return it to the refrigerator to keep it from going bad.

However, if the food won’t spoil and there’s no real need, it is best to be strict and avoid putting it back in the fridge.

When it comes to bottles of drinks, like juice or soda, halacha is more lenient. Since drinks don’t have a fixed status, it is allowed to refrigerate them, even if they weren’t already in the fridge before.

From “Ach Tov V’Chesed – Daily Halacha” by Hidabroot