Good question. Hanuma is very powerful but not powerful enough to swallow Sun. There is no need or necessity for Hanuma to swallow Sun.
By seeing Full Moon in night, if we think that we can hold it with our two hands and play like a volleyball, it's not our mistake. From here it looks like that. If we go near, we will come to know its actual size.
From earth, in the morning, Hanuma thought that Sun is a fruit as its size is so small.
Here we should understand an interesting thing. Though we thought of playing with moon, can we or any human fly to moon. Hanuma flew to Sun as a boy. Any doubt about his power?.
Regarding construction of bridge to cross the ocean, it's not for him. It's for the entire army and other warriors.
In fact Hanuma requested Sitamma to sit on his shoulders so that he can fly back with Sitamma to Rama in minutes.
Such is his power.
Jai Hanuman.
Subhamastu