There are two basic ways to San Antonio, and neither is a "good" way. The main way is Interstate-35, which can be a parking lot, a construction zone or both most of the time. The back way is US-281, which is very nice and takes you through the edges of the Hill Country, but always seems to take a lot longer than planned. It depends on whether you want to stop at Buc-ee's every couple of hours or not. (The back way has German food and pie.)
On I-35, you can stop at Slovacek's, which we only know about because they sponsor the Texas Bucket List TV show. So, one trip to Hillsboro for a Pirate Festival, we dropped in, and now it's a regular stop. You just can't go on the way out of town, because if you're loaded up with kolaches and sausages, you want to be heading towards a refrigerator. I-35 also has the advantage of having Buc-ee's all the way down to San Antonio (Hillsboro, Temple, New Braunfels.)
On the back way, Dutchman's Hidden Valley will always be a place I remember because I took one of my girlfriends there while I was in college. We drove and drove and never found it, so I assumed it had closed. I didn't realize it wasn't on the San Antonio end of US-281, it was on the Hico side. We were only about 170 miles away, so not exactly a short jaunt. The Bluebonnet Cafe has great pie - which you should order first, in case they run out. We went there one trip North from San Antonio and managed to arrive just as the Sunday Church crowd arrived. It was busy, to say the least.