Most truck stops will have a sign that says no consumption of alcohol on their property.
Many drivers have opinions on this. A lawyer familiar with the topic is likely to be your best source of information regarding this topic.
I think there is a lot of interpretation and gray area to consider.
This is not limited to whether it is technically legal or not but also what problems consumption could cause in various circumstances.
For instance... you are in a truck stop. Someone hits your truck. You get out to talk to police and alcohol is on your breath.
What happens? Not what is supposed to or should happen. What is likely to actually happen?
Of course you could do 'what ifs' all day. So you have to really think about the risks that you are comfortable taking regardless of the responses that you get.
What ways can you increase the chances of problems and what ways can you decrease the potential for undesirable outcomes.