Looking on the internet deeply has found these results:

what are u doing is the most popular phrase on the web.

what u doing 1264,000 results on the web	what are u doing 1587,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
She's doing her dissertation on it at Catholic U. Now u're doing it to me, too. The only one doing well is the guy who rents u What the USA and the? U are doing their best to save are the profits of the steel industries. turns and going through all sorts of contortions in relation to the whole nuclear issue. Recently the German Government has been doing U Joh n, I've been doing some u n iq ue calculations recently. U're doing a gamete micromanipulation on Friday.	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

what u doing

1264,000 results on the web

what are u doing

1587,000 results on the web

More popular!

She's doing her dissertation on it at Catholic U.
Now u're doing it to me, too.
The only one doing well is the guy who rents u
What the USA and the? U are doing their best to save are the profits of the steel industries.
turns and going through all sorts of contortions in relation to the whole nuclear issue.
Recently the German Government has been doing U
Joh n, I've been doing some u n iq ue calculations recently.
U're doing a gamete micromanipulation on Friday.

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.