Don't go chasing fuel prices off your route, the 10 cents per gallon is not worth it. You will burn that much looking for the fuel and you could have filled up and been 25 miles down the road by the time you complete the task. Bite the bullet and fill your tank. Top off for diversion if you need a diversion. If you intend on having a meal, accomplish both a fuel stop and a meal at the same time. In other words; every time you exit the highway, perform all the task at hand during that stop. Pulling "off and on" takes time and fuel. Next time you are driving note how much time it takes to go through the intersections, accomplish a task, go back through the intersections and get back on the highway. Less exits equal more forward progress.
Say no to foods that have carbohydrates. Carbohydrates will make you tired even if you are not a diabetic. Carbs are for hiking not driving. They make you feel good, until your insulin spikes then your eyes get heavy. You do not have to be diabetic to experience this.
Get a nice thermal coffee cup, I have a Yeti, it keeps cold, cold and Hot, hot. Its stainless steel, and easy to clean, I keep something caffeinated in it all the time. Coke Zero is good for me, it taste like a cola and has 0 carbs and it is caffeinated. If you drink coffee with creamer put real cream in it, rather than creamer, creamer is sugar with whitener. Sugar is a carbohydrate and makes you sluggish. The Yeti holds three cups and will keep coffee hot all day and will keep a soda with ice all day.