Many places serve food late (after 9 PM)  in Savannah particularly Friday and Saturday.

McDonough's (http://www.mcdonoughsofsavannah.com/) serves a full menu til 2:30am every day. Full menu includes everything from breakfast to fish & chips to steaks. Hands down one of the best burgers in the city. 

If you want a slice and a beer until 1am on a Friday or Saturday night then Vinnie Van Go Go’s is your place. Great big slices, freshly made ... a great late night snack before bed.  

 For quality pub food, Kevin Barry’s Irish Pub is a top recommendation. The menu is self explanatory and everything goes great with a Guinness. They serve till 2 am every night or depending on the mood of the bar.

After 2 AM/Last Call, Sweet Melissa's Pizza on Congress and Whittaker (next to Hang Fire and across from Circa 1870) is one of your only option unless you have a designated driver.  The food quality is what you would expect for a small town dealing with the drunk-overflow after closing time, but if you're not picky, this place is a godsend.  It might be reheated, it might be greasy, but it could save your life.  Remember to push water, you lush!  The burgers are a no-go, they help no one, especially someone coming out of the bars after a serious session.

 Sushi Zen (which used to be on Whittaker where the Cuban Cafe is now) moved to a location out on MLK and Congress.  They serve standard utility-quality Asian food until 5 AM,  so as long as you don't expect high cuisine, it could work if you're looking for something other than pizza. Remember to drink water!

The old standbys of Denny's, iHop and Waffle House require a car to get to, all on Abercorn in midtown (between the Oglethorpe Mall and the Publix supermarket).  Please have a DD if you go for this option, as Savannah PD will be actively patrolling for drunk drivers.