Fasting means to endure hunger and thirst and from things that cancel. Including when you do things that are legally permissible even though they are permissible, it is better to avoid them so as not to reduce the reward of fasting. Compiled from CNN, the following are makruh in fasting that should be avoided.
Gibah
Fasting is not just about holding back thirst and hunger. In fasting there is an obligation to guard the tongue from actions that invalidate it, including backbiting. But in fact, gossip or gossip is difficult to avoid and indirectly we often do.
As explained in Surah Al-Hujurat: 12, which means: "O you who believe! Stay away from a lot of prejudice, verily some of the prejudices are sins, And do not find fault with others. Is there anyone among you who likes to eat the flesh of his dead brother? Of course you feel disgusted. And fear Allah. Verily Allah is Most Accepting of Repentance, Most Merciful."
So, during fasting it would be better if we both refrained from giving up or talking about unnecessary things. We'd better replace it with useful activities such as reading the Qur'an.
Excessive Gargling
In fact, gargling is permissible when fasting, as long as it is not excessive or intentionally swallowed. The ruling is makruh when excessive in gargling while fasting is based on the words of the Prophet Muhammad SAW to Laqit bin Shabrah:
"Be serious in rinsing your mouth and inhaling water into your nose, unless you are fasting."
Food Tasting
Tasting food while fasting is makruh, as long as the food is not swallowed up to the stomach. Except in an emergency for the benefit of small children or sick people. However, if you taste too much food until it enters the stomach even a little, then this can invalidate the fast.
Toothache
Even though it doesn't break your fast, you should be more careful when you brush your teeth while fasting. The reason is, if water or toothpaste gets into the throat, this can break the fast.
As explained in the following fatwa from the fatwa council of Al-Lajmah Ad-Daimah 25/25:
"There is nothing wrong with using toothpaste with siwak because it does not include eating and drinking, but one should not use it excessively because it is feared that some of it will enter the throat."
Gulped
Swallowing saliva is forbidden for those who are fasting because it can cause saliva to be swallowed accidentally. This of course can invalidate the fast and can reduce the reward of your fast.
Of the five activities above, which one do you do or even often do?