If you have insurance, use it.
If you have AppleCare Plus - use it
If not, get a used phone off Swappa, or take the Phone into an Apple store to get an out of warranty exchange
|iPhone 6 Plus: $329|
|iPhone 6: $299|
|iPhone 5s, iPhone 5c, iPhone 5: $269|
|iPhone 4s: $199|
iPhone 4, iPhone 3GS, iPhone 3G, Original iPhone: $149
There is not much else to do at this point, it is gone. Since you do not know what other internal damage was done, I would not even try just a screen replacement.
It's most likely toast - 24 hours is not really enough time if it was totally immersed - it may need days rather than hours in the rice, and if the internals are already fried....it's gone. You can try more time in the rice, but having had the phone on if it is not completely dried out may have done permanent damage.
We assume the sink was full of water.
Turn if off immediately and do not use it for a while.
Take it to a service center to open it up, dry it off and test it out.
If printed circuit boards and electronic devices are OK, replace screen and probably the battery as well.
Otherwise, you are in need of a replacement phone.