As contractions the difference between whaddya and waddya
is that whaddya is what do you while waddya is eye dialect of what do you|lang=en.
whaddya
English
Contraction
(head)
(slang) what do you
:Whaddya think of my new dress?
Usage notes
*Whaddya is used only to form questions.
waddya
English
Contraction
(
en-cont)
(informal)
- Waddya want now, kid?