Because I have been drinking a lot of MiO, I've got a lot of those reusable bottles. :). You know me -- hug a tree; reuse all the plastics before making a scary landfill addition. I've been this way since high school 20+ years ago. OMG I'm getting old, huh?
Perfect for travel sizes -- I've been trying to come up with an exhaustive list of what can be put into them, though I haven't seen but one idea this far -- personalized hand sanitizer gifts. The lady who did that did a really lively job. If I can find it again, I'll share the link to her site.
The bottles only hold 1.6 ounces, so they will satisfy the TSA. Just don't peel off the label marking the size. Some of them have a problem with that. Some people need to get a freaking basic education on liquids volume.
Toiletries for Travel:
Mix-your-own MiO flavor combos
Lemon / fruit juice
Liquid B vitamins
Coffee flavoring syrup
* Whenever my family goes camping, we end up spending too much money on brand new bottles of ketchup, mustard, and mayonnaise for hot dogs and hamburgers. Of course, we never use them up on the trip, and that's how my sister's fridge ended up with 5 bottles each of ketchup and mustard, and several jars of mayo that went bad. Besides, that stuff takes up a lot of room in a cooler for the small amount we use. Forget backpacking with those things. Buying smaller bottles and jars is a ripoff as well.
Yeah, I know it's an environmentally geeky post, but that's just me. ;)