Pretty much anything that comes in a gelatin capsule can be dumped out and taken as a powder. You may have to experiment a bit to make it work but it can be done. Most common problem will be powders that do not mix/dissolve in water. Usually mixing in hot water as a tea will circumvent that problem. Adding honey or other sweeteners will sometimes help if you still have a problem with dissolving.
I will often simply open and dump a capsule in my mouth then chase with water or tea. Be careful and use common sense as some things that come in capsules are designed to be safe for the stomach but are a bit caustic in the mouth.