What I did on my recent vacation (to Utah, where we were hiking for most of the day) was to eat breakfast in the morning. Most of the places we went had some kind of eggs as well as either bacon or sausages. I’d grab some butter and put it over my eggs along with salt and pepper. (You need to up your salt intake on keto!)
We’d then go do our daily activity, which as I mentioned earlier, was almost always hiking. We would often be out for most of the day. I’ve gotten accustomed to hiking (or mountain biking) for long periods without food.
When we got back, we’d go to dinner where I’d choose things to eat as described in my earlier post.
For snacks (or for the occasional breakfast or dinner when I couldn’t find anything suitable), we also brought with us some macadamia nuts, pecans, tins of oysters packed in olive oil, and some Rx Bars. (My favorite Rx Bar is Chocolate Sea Salt. It has a few too many carbs to be truly keto, but I tested my blood each day that we were on vacation and managed to stay in ketosis even when I ate up two or three a day. I’m guessing that I burned enough of the carbs during our activity during the day.) My wife had also brought with us (in a cooler) some of my favorite savory fat bombs. There were some days when I was able to eat the stuff that she brought along for me in place of going to dinner.
With regard to the fat bombs, if you don’t have it yet, you should get this book:
https://www.amazon.com/Sweet-Savory-Fat-Bombs-Delicious/dp/1592337287/
I don’t really care for the sweet fat bombs, but I really enjoy the savory ones.