In frying pan at home, add butter and heat on medium-low.
Whisk eggs in a bowl and pour into pan to scramble adding salt and pepper to taste.
When eggs are done, add to a holding plate.
In same frying pan (clean if necessary), fry up the sausages with a bit of water in the pan. Flip and fry on all sides until lightly browned and cooked thoroughly.
Cut potatoes into small pieces and add to either a frying pan with butter and fry until cooked through, or bake in oven with butter and a bit of salt and pepper until done.
With a large piece of heavy-duty foil, add all your cooked goodies in the center and fold over so that it forms a solid package with no gaps or openings. You can keep it in the fridge or cooler until it's ready to be used.
To Cook:
Start fire or keep one going that is already started with the intention of creating coals which will be your heat source. If possible use harder woods that produce hotter coals. For reheating these foil packs you don’t need as many coals as you would if you were cooking them from scratch. Also, it’s very helpful to use a grill or grate of some kind over the coals so as not to burn your food!
Place foil pack on grill/grate and make sure it is not too hot.
Arrange coals with tongs if needed. Place some coals on top of the foil pack as well as smaller hot rocks if you have any.
Heat for 10-15 minutes, checking once or twice to see if it heated up enough. Inspect the with fork or tongs for doneness.
Take off coals and open up your foil pack. Check the bottoms especially as they can easily burn.
Notes
Make sure not to overcook your eggs at home since you are reheating over somewhat high heat. Also ensure your potatoes are nowhere close to burning.
I recommend heavy-duty foil as it is larger (wider roll) and of course less likely to tear since you are handling it quite a bit.