AgroI'd equate it to volunteers at a soup kitchen getting a cup of tea at the end of a shift. Maybe just a glass of water. Maybe a small glass of water every other shift. Tap water. Are you still okay to claim this doesn't make them volunteers?
edited for clarity
If they are asking for it, then they are not volunteers.
If it's just your intention (as an owner/organizer/the person who brought them together) to support them this way, then they are still volunteers.