What bhak means
bhak is the cut between friends. The laugh after it is what makes the cut safe.
The cut
bhak, also said bhakk, is Hindi college slang. Get lost. Shut up. Yeah right. Between friends it is amused disbelief. It ends a claim without starting a fight. You say it when someone is telling a story you both know is only half true.
It is clipped, like the start of the word luck. Said in a flat, and in a group chat, and at someone who is doing too much.
The other word
bhakt is a different word. It means a devotee. On the Indian internet it became a political insult. One extra t and the joke is a side. This is bhak. There is no devotee joke here, and no side.
If a caption needs the other word to be funny, it does not belong on this site. The cut is at a friend, about a claim, with the laugh still attached.
Why the laugh is there
A bare bhak at a stranger is rude. bhak, then a laugh, is how you know someone. The laugh tells them they are still in. If you cannot hear the laugh in the picture, do not send the cut.
You already type it this way when a friend is performing. The picture is that, with their name on the line, sent while the moment is still true.