You would probably expect that one of the conditions of probation (technically - community supervision) is that you not drink or use drugs. Drinking would be especially important for someone on probation for a DWI case - especially a felony DWI. When you are on probation you are required to submit urine samples from time to time to make sure you aren't using. Breath tests might also be adminstered.
In Waco and McLennan County you might get a couple of chances - as long as you are doing well on everything else. The probation officer might impose some sanctions, or require additional classes. If you do it again though, it will be referred to the District Attorney's office and a motion to revoke will be filed. Because that's the experience I've had as long as I've been practicing, I was completely suprised to learn that may not be happening in Dallas County.
According to an article in the Dallas Morning News one judge has called for an audit of all the cases in her court after she found 34 cases where probationers had repeatedly failed drug tests, or been caught drinking, and the court had not been notified. That included the case of a man who was on probation for a felony driving while intoxicated case.
In case you are thinking about moving to Dallas and having your probation transferred there, the Dallas County probation department has already implemented changes to correct the problem. So it doesn't look like you will be able to get away with it in the future.