Spent a week in Austin last spring.
Can vouch for Salt Lick BBQ in Driftwood TX. Wonderful. BYOB!
Have to do Voodoo Donuts, preferably about 3:00 AM. Check out the long thin donut with chocolate frosting.
If traveling north or south of Austin make sure you stop at Buc-ee’s. Kind of a combination of a handful of Wawa’s, a few 7-11’s, a Sonny’s and several I-Drive over the top souvenir stores. 120 Gas Pumps! A wall of Jerky!! (There are actually a couple of these coming to Florida in Daytona and Ft Myers)