Eating away from home; what are some of the best snack foods to have in your hotel room?

One thing to look into...many hotels will put a fridge and/or microwave in your room if you request it ahead of time. My husband travels a lot for work, and will call the hotel a few days before arrival to ask. Most are able to do this, free of charge. That would then open up a variety of options for you...yogurt, cheese, hard-boiled eggs, microwave popcorn.

If they can't do that for you...there are a lot of fruits and vegetables that don't need refrigeration, especially for relatively short periods of time. You could get a jar of peanut butter and smear a little on an apple or some celery. A lot of hard cheeses don't necessarily need refrigeration. A pre-packaged bag of popcorn usually has relatively few calories. Snack bars/protein bars/granola bars if you like them and the calories work for you.

If you do end up getting a fridge, that would totally make your life easier. I'd recommend fruits in this case, especially in this weather! But I've been at plenty of hotels where this was not the case. Some fruits are alright at room temperature such as grapes, apples, and berries. You could bring/buy nut butter with you too to spice it up a bit.

You mentioned nuts and this is what I usually go for; the plain nut mixes. Still high fat; but healthy fats. Depending on where you are, there are maybe some healthy oat bars available, although I know some of the bought ones are packed with sugars. Also something worth considering making at home and taking with you, if you're willing to do this extra step.

A more exotic option could be those sea weed crisps if you're into that and crave something savoury. Dry crackers and saltines also come to mind which are not terribly unhealthy, though not very exciting or nutritious either.

If you have a kettle, those instant oat/porridge pots are great. You could even buy some bananas or berries to add to them. Similarly, there are some grain lunch pots available which are either quinoa, beans, or lentil based with some spices or veg inside. Those are reasonably healthy too, given your situation.

I think a lot comes down to your tolerance and if you're willing to prep at home and take it with you. That would open up a lot more options for you.

If you get the fridge, hummus is one I like to take along with veggies- snap peas keep and travel pretty well. Also some of the vegan jerky's are a good lower calorie snack.
Not super healthy but a low calorie option are the Gel type pre-made jello cups. The sugar free ones are 6 calories. If they say "gel" they don't usually contain gelatin